Help me build a (relatively cheap) computer!

My friend is into building computers and I told him that I wanted a gaming machine. We have different priorities, especially when it comes to money, so he came back with specs that put my proposed machine at like $2000. He does know I put huge preference for bang for the buck type deals, but 2 large is out of my price range. I would like to spend around $650 (cpu only). Am I being unrealistic? I’m willing to bargain shop (or abuse company procurement office discount, or borrow from IT dept) all day to whittle down the price. I plan on playing Doom3 (I’m a sucker for that game), Civilization (which I actually like better), downloading stuff, and photoshop. I had my friend re-do his specs with my budget in mind and this is what he came back with:

Athlon 64 Processor 3200+ with Hyper Transport Technology @ 199.99

RADEON X800 XL 256MB GDDR3 PCI-E x16 Video Card @ 299.99

80GB Serial ATA Internal Hard Drive @ 64.99 x 2 … (129.98)

X-Finity 500 Watt ATX 12V Power Supply @ 79.99 (49.99 after rebates)

Case: get from work, or from my other friend (who most likely got it from work :))
ASUS K8N4-E DELUXE Socket 754 NVIDIA nForce4 ATX AMD Motherboard - Retail @ 104.00 (refurbished @ 83.00)

Ultra 512MB PC3200 DDR 400MHz CL3 Memory @ 64.99 (34.99 after rebate) – x2

Diamond Radeon X800 XL / 256MB DDR / PCI Express / DVI / VIVO / VGA / Video Card @ 304.99 (274.99 after rebates)
Maxtor 200GB L01P200 Ultra Series 8MB Buffer UATA133 - Retail Hard Drive Kit @ 69.99

There’s like two Video cards in the specs above, and I can’t decide which one I want. Like I said, I want to play Doom3, but I also want my cpu to last more than a year. Is there any place else I can cut? Do I need 80GB hard space (or is it one those ‘you might as well get it?’) Thanks for the advice.