DS3 only has 1 pcie slot, Infinity has two, DS3 is a better OC'ing board though. Infinity is also a bit more expensive, not much more. Depends on how much you want to OC, if you don't plan on doing an extreme OC, Infinity is good, but DS3 is better for pushing the conroe.
C2D E6600 @ 3.15ghz w/ 1.35 vcore
2GB G.Skill DDR2-800 (4-4-4-12)
XFX 7600GT xXx