Hmm, I'd say- (keeping it general)
CPU- Core 2 Duo
Motherboard- I definitely recommend Asus
GPU- A 7000 series nVidia card (ex- I have a 7800GTX)
HDD- There's a sweet newegg deal right now, buy a 500gb HDD and get a 250gb HDD all for $209 (link
RAM- Idk..atleast 2gb
PSU- Something around ~500w would probably be efficient
Case- I have a Thermaltake Tsunami..I love it...little expensive though.
p.s. I have some comp parts for sale, you might be looking for more though. I have a-
CPU- Pentium 4 650 3.4ghz with h/t
Mobo- Asus P5ND2-SLI Deluxe (godly)
PSU- Thermaltake 680w (it's a beast)
Sound Card- Creative Labs Audigy2 ZS PCI
Wireless Card- Netgear 108mb/s PCI Card
..possibly some other stuff.
Just PM me if you're interested...