I do work with 3DS max, After effects, Photoshop, C++ scripting, Web Design, and Gaming, I'm essentially trying to make a super computer because of all that, and I figured two i7's could be SLI'd
You'd have to go Xeon e5-2000 series or opteron to do dual CPU. And since none of these come with 6 really fast cores like the i7-3900s, you'll need to go 8+ slower cores to get there. Dual E5-2660s would be about the same as dual i7-3970K's, but a little more expensive.
You could also go dual AMD 16-core Opteron for a little cheaper and get similar performance.