You might want to check out www.dvnation.com
to see how they configure their Ramrod storage system, and how they put 64G of ram to work.
Does garbage collection work on a ssd raid currently?
Why all the GPU multiple horsepower? Running a 4K projector and gaming on it?? What other tasks will the htpc be doing? Rendering?
How much rack space do you have? You could split the drives to a second case, each with their own power supply. Two Ebay 121060721807 and two
power supplies would be cost effective, if somewhat rack space hungry.
Water cooling saves me money too. My desktop has a 3930K with a moderate overclock to 4.2 Ghz, cooled by a Corsair H100. I appreciate the quietness,
and how a $440 Craigslist cpu, plus a $90 water cooler (on sale) puts me into 3970X performance territory. The computer runs a 240G ssd boot/program drive
and a single 2TB green drive and is very snappy.