I have been playing with used workstations over the last few months. It has produced a whole lot of posts because of various issues as some of you already know. I thought I would post what I learned in case anyone would like to play with one as a cheap gaming PC.
My first one was a Dell 9020 mini tower. Looking back at 200USD I payed too much. It came with an i7-4790/2x8gb ram/DVD driver/1TB SSD which is a generic drive with Windows10. I had problems with the board having a bad ram slot but the vendor shipped me a new board. Still I spent a long time dealing with the ram issue. The case is cramped and I had to mod it to get a video card into it. Also, if you want to add a video card you need to replace the PS and get an adapter cable because it has some Dell MB power cable. I would not recommend unless you can get one super cheap.
I got an HP z240. It was only 130USD with an i7-6700/2x16 GB DDR4 PC2133/256GB NVMe drive/1TB SATA drive/K2000 video card. Not a bad price. It is giving a PS fan failure error at boot but the fan seems fine and it has been working fine so far. I had all kinds of problems with it hanging at boot when I first started working on it. It turned out that I had a USB external hard drive dock with 4 drives in it. When the dock was powered on the system tried to boot from that and was too stupid to bypass it when it couldn't find a boot drive. You can disable the USB boot option. I just turned the dock off at boot. You can get them with i7-7700's and i7-8700's which would be better if you someone is looking for a cheap gaming computer. I did not add a video card to it but if you want to you'll have to upgrade the PS and again get the adapter cable. You could put together a decent system for less than 400.00 if you shopped around.
I also got a caseless HP z420 with an E5-2695v2/4x8GB PC1866 DDR3/120GB SSD/GT710 video card for 160USD which was not a bad price given the PS was already replace with a Corsair 750w unit. Unfortunately the PS crapped out on me. But that is the risk you take buying used components. I through in an EVGA 850 I had laying around and everything works fine. I upgraded it with a 1TB SSD and and a 2TB WD red drive as well as 2 optical drives and used an old 5850 I had to replace the GT710. I probably should have left the GT710 in it. I'm not sure what kind of gaming performance you would get with a proper video card but given the low clock speed probably not great. I have been using it to transcode DVD's. It does a pretty good job at doing 2 at once. There are better options than old E series Xeons for gaming.
Last but not least is the Lenovo P520. I got one with a W-2145 for 230. There are a lot with w-2135's available and some with higher end W-21xx CPU's if you want to spend the money. It came with a 900w hotwap Platinum PS that has 2 8 pin power connectors so no need to pay for an upgraded PS. I had some problems with getting my RX6800XT working but it turned out to be my stupid error. I got 4x16GB PC2666 Micron ECC DDR4 for about 100USB. You could go with 2x16GB if you want to save money but you won't get quad channel memory. It only has 2.0 onboard sound so if you want better you'll need a sound card. It has a PCI slot and a PCEx1 slot. I had a Xonar DG PCI card on hand that gave me fits but replacing it with a PCEx1 version solved the problem. That added only 25USD to the build. It also has 2 NVMe slots on board which is nice. I added 2 1TB NVMe drives/2TB SSD drive/4TB SATA drive/Bluray drive and a hard drive rack so I can add another drive if needed. The CPU seems to run hot so reapplied the thermal paste which helped but decided to get a Noctua NH-D9DX i4 3U. From what I read it should use the standard mounting hardware so no need to pull the system apart to change that. You don't have to replace the stock cooler but it is a bit light and not designed for gaming. One problem I did run into that caused me all kinds of issues was when I first installed Windows somehow the install got deleted. Not sure how but it was. While I was playing with it, I switched the BIOS to UEFI mode. I had an old non UEFI video card installed that I use during build and with a non UEFI card you get no video output. Resetting to default BIOS setting doesn't help since UEFI boot is default. Adding the RX6800XT fixed that but again I spent a lot of time before I figured out that problem. I have not used the system yet for gaming but I would definitely say yes on this for a cheap gaming build. For around 350.00 plus video card/storage you have a nice system with a decent 8 core CPU and 64GB ram. The front panel has 2 5.25 inch external bays/USB 3.0 and an SD card reader which is also nice.
Now onto the Dell T5820.
My first one was a Dell 9020 mini tower. Looking back at 200USD I payed too much. It came with an i7-4790/2x8gb ram/DVD driver/1TB SSD which is a generic drive with Windows10. I had problems with the board having a bad ram slot but the vendor shipped me a new board. Still I spent a long time dealing with the ram issue. The case is cramped and I had to mod it to get a video card into it. Also, if you want to add a video card you need to replace the PS and get an adapter cable because it has some Dell MB power cable. I would not recommend unless you can get one super cheap.
I got an HP z240. It was only 130USD with an i7-6700/2x16 GB DDR4 PC2133/256GB NVMe drive/1TB SATA drive/K2000 video card. Not a bad price. It is giving a PS fan failure error at boot but the fan seems fine and it has been working fine so far. I had all kinds of problems with it hanging at boot when I first started working on it. It turned out that I had a USB external hard drive dock with 4 drives in it. When the dock was powered on the system tried to boot from that and was too stupid to bypass it when it couldn't find a boot drive. You can disable the USB boot option. I just turned the dock off at boot. You can get them with i7-7700's and i7-8700's which would be better if you someone is looking for a cheap gaming computer. I did not add a video card to it but if you want to you'll have to upgrade the PS and again get the adapter cable. You could put together a decent system for less than 400.00 if you shopped around.
I also got a caseless HP z420 with an E5-2695v2/4x8GB PC1866 DDR3/120GB SSD/GT710 video card for 160USD which was not a bad price given the PS was already replace with a Corsair 750w unit. Unfortunately the PS crapped out on me. But that is the risk you take buying used components. I through in an EVGA 850 I had laying around and everything works fine. I upgraded it with a 1TB SSD and and a 2TB WD red drive as well as 2 optical drives and used an old 5850 I had to replace the GT710. I probably should have left the GT710 in it. I'm not sure what kind of gaming performance you would get with a proper video card but given the low clock speed probably not great. I have been using it to transcode DVD's. It does a pretty good job at doing 2 at once. There are better options than old E series Xeons for gaming.
Last but not least is the Lenovo P520. I got one with a W-2145 for 230. There are a lot with w-2135's available and some with higher end W-21xx CPU's if you want to spend the money. It came with a 900w hotwap Platinum PS that has 2 8 pin power connectors so no need to pay for an upgraded PS. I had some problems with getting my RX6800XT working but it turned out to be my stupid error. I got 4x16GB PC2666 Micron ECC DDR4 for about 100USB. You could go with 2x16GB if you want to save money but you won't get quad channel memory. It only has 2.0 onboard sound so if you want better you'll need a sound card. It has a PCI slot and a PCEx1 slot. I had a Xonar DG PCI card on hand that gave me fits but replacing it with a PCEx1 version solved the problem. That added only 25USD to the build. It also has 2 NVMe slots on board which is nice. I added 2 1TB NVMe drives/2TB SSD drive/4TB SATA drive/Bluray drive and a hard drive rack so I can add another drive if needed. The CPU seems to run hot so reapplied the thermal paste which helped but decided to get a Noctua NH-D9DX i4 3U. From what I read it should use the standard mounting hardware so no need to pull the system apart to change that. You don't have to replace the stock cooler but it is a bit light and not designed for gaming. One problem I did run into that caused me all kinds of issues was when I first installed Windows somehow the install got deleted. Not sure how but it was. While I was playing with it, I switched the BIOS to UEFI mode. I had an old non UEFI video card installed that I use during build and with a non UEFI card you get no video output. Resetting to default BIOS setting doesn't help since UEFI boot is default. Adding the RX6800XT fixed that but again I spent a lot of time before I figured out that problem. I have not used the system yet for gaming but I would definitely say yes on this for a cheap gaming build. For around 350.00 plus video card/storage you have a nice system with a decent 8 core CPU and 64GB ram. The front panel has 2 5.25 inch external bays/USB 3.0 and an SD card reader which is also nice.
Now onto the Dell T5820.