Well, I've done it.  I put together my system Friday night, Saturday morning.  It's working pretty well.  I've run some comparitive tests in Vue 8 between my old PC and the new and the new is rendering between 2.5 to 3 times faster.  The only problem I'm having so far is that I can't render scenes in Lux with the GPU.  I get a runtime error.  I got those GTS 450 cards and have them in SLI mode.  I have the latest drivers so that's not the problem.  Lux renders just fine with the CPU.