I replaced my Nvidia 5900 over a year ago and it was old back then. A duo core computer, if you shop right on newegg, will cost you no more than 600$$ with at least 2 gigs of ram. That is, if your old case is capable of retaining the new MB, HD, Power supply, and Vid Card. Cases usually run at least 80$ for a good one.

[Linked Image]

[Linked Image from nodiatis.com]