I replied in your other same-titled topic posted in the Computer Help forum, so you may want to read what I posted. Thoughts from what I've read in this topic:
Your parts summary lacks crucial information to determine compatibility. For instance, you have a dual gigabit networking adapter included, but no information on the make or model of said NICs, or the the motherboard that they are included with, which might have led us in the right direction. As such, you can not be in anyway positive that these NICs will work under ESX.
My motherboard on my ESX box has two integrated gigabit NICs by Marvell, which are unusable under ESX, as they lack the driver support. The box wasn't originally built with ESX in mind, so I adapted it, and in the process had to buy 3 x Intel PRO/1000 NICs based on the e1000 chipset that do work with ESX.
The RAID controller is listed as SAS6iR, which a quick search for seems to suggest is a proprietary Dell RAID controller. I did a quick search and found a single post on the vm-help HCL list that suggested that it does work, but nothing conclusive whatsoever, and once again, there's no chipset information which makes conclusively determining compatibility very difficult.
4GB of RAM is pretty reasonable, provided you don't intend to run lots of concurrent VM's, ESXi will burn through 512MB easily before running any VM's, and ESX will burn through more than that, though I couldn't say how much more. Your CPU I would suggest is passable, and should do the trick, once again, provided you aren't running lots of concurrent VM's and/or putting heavy load on several VM's.
I can't stress this enough, you _MUST_ verify hardware compatibility for all relevant components or you risk being very disappointed and very pissed off when you've spent several hundred or thousand dollars on equipment only to find it doesn't work. ESX has very limited hardware compatibility, so you can't make any assumptions that your equipment will "just work", and that extends even to expensive high-end equipment.
Building an ESX server for cheap is possible, but just remember you get what you pay for, and if you're intending to turn this into a production server running several VM's, you may well run into trouble. Factor in expansion potential as more VM's are added and load on VM's increases as well, and you'll realise that depending on your aims, buying cheap may not be in your best interests, at least, not in the long term.
DaveSimmons: SCSI isn't really a requirement, in that it can run on SATA fine, though I believe this is unsupported and requires some tweaking. Realistically, you'll want a RAID setup backed by SATA/SAS/SCSI disks.