I think this new PC thing is doable by the end of the year... i'd essentially only keep my GPU I think, would cost around 800 or so... i'm trying to think if I am forgetting anything...
Boost your ram to 12 or 16 gigs. More games now are front loading ram and using 5ish gigs easy.
What are you going to SLI? Change your PSu to 750watt for wiggleroom and upgrade ability.
Micro ATX cases and boards are really small. I doubt you can fit an SLI setup in there. Your cards will be covering the other slots so no soundcard,or other PCI slots and running SLI your case will heat up a lot.
I would suggest a midtower case SLI.