Great Post! I would change your x5650 assumed price though. I bought a HP DL380 G6 with 2x x5650 Processors, 16GB Ram, and 2x 146GB SAS 10k HDDs for 250€ (Approx $310 USD) last month.
Its loud and not as efficient as modern servers but it runs 24/7 no problems
RE: SUPERCOMPUTERS: Titan vs BOINC vs F@H - Counting FLOPSs in a FLOPS – part 3