I agree, use the slower 2.66 cpu and clock to 4ghz, with the EVGA mobo and dual CPU's it should steam - remember, the cpu is seriously important for RED playback, the GPU does nothing. The GPU accelerates effects only - so you need the fastest and max cores possible to get multiple RED streams in real time. My system has 4ghz overclock from a 2.66 i7 - if I turn off the clock it barely plays quarter res RED4K, overclock on, plays half rez RED4K no problem. Buy a pre built mobo cpu ram cooler overclock package with guranteed performance, most decent companies will recomend psu's depending on graphics cards you want to use as well. Then stick it in a box and off you go - yeah the H50 water cooler is great too!
Also don't mess with anything less than 6GBs sata III SSD for system drive. believe me, with Windows 64 bit, the whole experience becomes rock solid, almost impossible to crash.
Forget the Supermicro mobo's as far as I know they never OC.