It depends a lot on your budget and preferences too... (mind you I'm no gamer)
I've been shocked when I say how easily and how much you can OC a Socket 754 Sempron 3100+ to like a equiv rating of over 4000+ (being faster than a Athlon 64 that costs leasily 4 or 5 times as much, and the socket 754 boards are cheaper than the 939 ones). A LOT of bang for the buck.
If I was buying a new PC right now (I might very soon too), here's what I'd pick:
-ASUS K8N-E DELUXE S754 NFORCE 250GB 175$ CDN (~135 USD)
it's got 6 SATA ports, dual RAID, 8 channel audio, firewire, 8 usb 2 ports, gbit ethernet...
-S754 Sempron 3100+ 170$ CDN (~140 USD)
-2x 512MB DDR400, 100$ CDN Each (~80 USD Each)
-2x 200GB SATA 8MB HD (Maxtor, WD, whatever's on the special-du-jour) 135$ CDN each (~107 USD each) - nice and cheap sataraid0 setup
-Pioneer DVR-108 (if you need a new fast DL DVD burner) 100$ CDN (~80 USD again)
-Radeon 9600XT 256MB 225$ cdn (~180 USD)
-A uh, something, ok case with decent PSU, 60$ cdn (~48 USD)
For 1200$'ish CDN (~950 USD), you get quite a nice rig. It'll do anything you try, and fast. Lots of CPU (OCs nicely), lots of fast storage, fast DL DVD burning, nice gfx card... I'm most likely going to buy this exact system very soon (other than with a cheaper vid card - most likely 9600 pro - as I don't play games) Try to come up with more value than that

[edit] (there's always someone submitting a post as I'm typing mine!) If I wanted to have a separate sound card, I'd definately pick a MAudio over anything made by creative, but I guess it's because I'm coming more from a HTPC background rahter than gaming...