2 hd are only needed for RAID, 1 is fine and seagates are nice - 5 year warranty nowadays. Their SATA drives at least are real quiet too, so are the samsungs.
Do whatever you need to do to get the 6800GT, it is a 3-4 times better than that 9800 Pro.
If you really don't want to go there, at least get the 6800 plain - it's only $75 more I think.
Get only one stick of memory and order one from newegg - there it is $75. Saves $40.
The motherboard comes with gigabit LAN, so I think you can use that and skip the Network card. Saves $39
Get 2 years of on-site support. You will probably never need it and after 2 years your machine will be obsolete and you will be wishing it broke down. Saves $20
I would say skip the sound card for now since that motherboard has on-board audio, see how good it is. Saves $96
As far as the motherboard, I would try to go with some recomendations from other posts. That builder's guide that I mentioned earlier has some of the best ones listed in the mid-range build. You could start with the list from monarch, that would narrow it down from the beginning if you are getting from them. Search for "754" in General Hardware and Motherboards forums. Look for recent ones, because there are still boards coming out. There are 2 general flavors: one has the nForce chipsets, the other has the VIA. nForce was ahead last time I looked, with on-chip firewall, etc. When you narrow it down, google for "that board name +review" and read up.