I think just about anyone around here will recommend an 8800 card:

http://www.newegg.com/Product/Produc...82E16814130318

I'm less familiar with the different versions (gt, gs, gts, etc) and don't personally own one, but I've seen these threads enough before and the recommendations come from trusted sources too many times to not throw it out there myself. They are out with the 9xxx series now, but I've heard those can be unstable atm, whereas the 8800 is a rock solid card that is a guaranteed good choice. I intend to upgrade to one myself sometime in the near future.