One of my builds is almost a duplicate of what you picked (used the LX). The PSU used in that build was similar to this: http://www.tigerdirect.com/applications/SearchTools/ite...
No problems so far and very quiet.
As far as the Z77 vs the Z68 there really isn't much of an improvement at this time. The z68 will probably do all that you're looking to do.
Did I miss something? I thought his form said NO sli/cfx? Did his form say 2 7850's? If not then why would he need the second Pcie slot? I based my recommendations on what his form actually stated not on what I wished it stated.
seasonic 520W 80plus bronze the one ith M12II something should be more than enough for your needs but go 600/650W if you want more head room just in case you want to add other stuff and overclock like a volcano or something.
Though this seems to have turned out well, I'll contradict anyone who says no Xfire. It's a great, economical upgrade, and there's no reason to avoid it.
I agree with you but that's not what the OP was looking for. If I can change someones mind toward a better part or point out their errors in components or solve a problem than that's all I can hope for. I know that you are only doing the same.