I need a video card, of a different brand, that is comparable to the Nvidia GeForce GTX 550 ti.

I have been trying to get my computer back up and running for a week now. I installed the Nvidia GeForce GTX 550 ti (as an upgrade from a dead Nvidia GeForce 9800GT) but none of the video drivers will work. Default windows driver kind of runs it, but whenever I install Nvidia's drivers, new and old, I get a black screen on a normal boot right after the Windows loading screen. I can boot in safemode without issue, which tells me its a driver issue. Others on the Nvidia forum have reported this with different computer hardware and using the GTX 500 series.

Ive tried getting the drivers to work on both XP 64-bit and Windows 7 64-bit but get the same results. I meet all other minimum requirements.

I have been out of the hardware world for too long and dont know whats good and whats what out there. Could someone point me in the right direction to a video card that is just as powerful as the GTX 550 (1bg built in) but a different brand than Nvidia?

I hate to stray away since Ive always had reliable cards, but I need a working computer.

Thanks in advance!