570s are fine.
Not sure what these others are refering too. nvidia's architechture favors more complex floating point operations, whereas AMDs architecture favors less complex integer operations.
Asuming your want to run one large display, 6950's or 6970s might have been a better option since they have 2GB of vram.
Video Card Possible Alternative
Is there a particular reason you chose ASUS as your brand rather than say, EVGA? EVGA always has amazing warranties (though be sure to pick up the ones with the serial codes ending in -AR). However, if warranty is not of an issue, I can't really complain with this choice. Nice, though I would argue that you might enjoy Crossfire 6970 2GBs much, much more, especially with Eyefinity and a multi-display setup in mind (you get almost a gig more VRAM per card, plus... Eyefinity... THREE big, 1080p, widescreens. Need I say more?)

2 fans are better than 1 dude![]()
6970& 6990 outperforms any nvidia card at high resolution
nope personal experience..and he will have 3 monitors like me..so yea i know 6970 > 580 at high resolution there are plenty of benchmarks too ... and price is cheaper for ati esp since u can buy a 6950 and convert it to 6970 annd save even more money
http://www.techspot.com/review/348-amd-radeon-6970/page5.html
http://www.techspot.com/review/348-amd-radeon-6970/page8.html
http://www.techspot.com/review/348-amd-radeon-6970/page10.html
http://www.techspot.com/review/348-amd-radeon-6970/page11.html
Look at the results for the GTX 580 @ 2560x1600, 8xAA. Like I said, the GTX 580 is the superior card that only loses its advantage in multi-card solutions where GPU memory becomes much more important.
Nvidia still has the king when it comes to single-GPU solutions at all resolutions. AMD has a compelling argument for multi-GPU setups though.