Seeing as how D3 shouldn't be that taxing, this computer will eat it alive. i5 2500k and GTX 570 with the 8gig 1600 Ram will utterly destroy all of D3.
I myself recently bought an i5 2500k, 8gigs of Ripjaw 1600, and a GTX 560ti. I got Dragon Age 2, set everything to max, and it doesn't even hiccup. Didn't even try OC'ing yet, no need until I see a drop. Unless D3 has some intricate programming and graphics from that perspective, I doubt either of us will need to worry about D3.
I'll try to post specs later of mine in full, or just a picture. The only thing is my computer is set up so I can't see into it despite it having a view inside. Oh well. Still been amazing so far.