Agree that the motherboard and PSU are fine for GTX 570 SLI, even if I wouldn't have recommended that Raidmax PSU.
The only difference between those two cards that I can see is the length of the warranty;
the 012-P3-1573-AR has a "Limited Lifetime warranty with registration within 30 days of purchase"
and the 012-P3-1573-KR has a "3 year limited warranty. Registration is recommended".012-P3-1573-AR product page012-P3-1573-KR product page