Although, 2 580s, on the other hand, outperform one 590 because of the downclock of the GPUs on the 590.
Either a single 580 or a 590 would be great for games and a 590 would definitely be better. The more power you have the more you can crank the details, AA, AF, and AA transparency at a given resolution.
I like the high quality/high performance capability.