Ah okay well Tacos does have some good suggestions with the A64 and nvidia 7600. One way to save money (sometimes) is to purchase a bare bones system that would include the motherboard, case, and power supply in one package. Since it seems unlikely you'd overclock, you coud purchase a moderate to budget end product from a high quality maker like ASUS.
This one or something similar may be suitable:
http://www.newegg.com/Product/Product.asp?Item=N82E16856110055
I used to play City of Villains, World of Warcraft, and Eve Online on an A64 3200+ based system with an ATI x800 video card. Those games were somewhat disappointing on that system. But I was running it before I really knew what I was doing. In hindsight I could have overclocked the system, or turned down the graphics settings in the games, and things would have been alright.
Fry's is a computer store chain with locations mostly in California (where I live) but also in other parts of the U.S. They have weekly motherboard/CPU combo sales. I was going to suggest you be alert for those if there's a Fry's location near you. But really, online sellers like newegg, chumbo, zipzoomfly, and mwave all have just as good deals, and much better service than Fry's, which is legendary in Silicon Valley for its surly employees.