Well, you might want to read the reviews first. there was a GTX 5series that the reviewers hated. the 550 might have been it. Only reason i recommended the 560 Is it's a good price/performance card. I've had good experience with the GTX470 and I currently own 2 GTX580 in SLI. The 560 is suppose to be as good or better than the GTX470. You might also want to look into the ATI cards.

good luck with the purchase!