I would seek some expert opinion. I'm putting together a new PC (in Shuttle SB81P Case w/ Intel P4 3.4, 1GB RAM, 200GB Seagate HD).
Now I need to decide which graphics cards to purchase - here's the shortlist of candidates:
(1) ATI All-In-Wonder RADEON X600 PRO Video Card, 256MB DDR, 128-Bit, DVI/VIVO, PCI Express - $219
(2) PowerColor ATI Radeon X700 PRO Video Card, 256MB GDDR3, 128-Bit, DVI/TV-Out, PCI-Express, - $219
(3) PowerColor ATI RADEON X600 XT Video Card, 256MB DDR, 128-Bit, DVI/TV-Out, PCI Express - $179
I am building a similar system to the one your describing sometime tommorow. It will have the same CPU that you have, but I am going to use a GeForce 6600GT. If your interested in the performance of this card I will be happy to let you know tommorow how things turn out.
Of those choices, the X700 is by far the fastest gaming card.
The X600 All-in-wonder is a slower gaming card, but it offers video in/out and a TV tuner, so it's the better choice if you want a "media center" computer instead of a gaming machine. (although the X600 will do a decent gaming job as well)
The 6600GT is another very good choice for gaming, about the same price as the X700 PRO but a bit better performer.