I built a budget gaming system for a customer. I was not too happy about the budget he had but we built it for him anyways.
The video card we used is the Sapphire ATI HD 4650 which costs like $75 Retail
We installed warhammer to test it and I was seriously amazed by how awesome it performed. Can't crank up the graphics to max like I can on my 4870x2
No video lag or any problems at all.
The machine has an AMD 6000, Asus M2A-VM with 3GB Memory, what a bargain for a gamer!
Truly amazing how cheap good technology is becoming.