i, at one point, was going to build a SRx monster, as the main server for my render farm. but careful considerations drew me away from building it.
these are the costs: mobo (~£450); 2x 2011 xeon's (~£2900); 64gb memory (~£500); plus extras (GPUs; SSDs; opticals; cooling; IO devices; etc) = a ball park of £6000+.
this would give me a 16core (32threads), @3.1GHz, rig.......and it would ONLY be the server.
for £6000 i could get 6x (SIX) i7-3930K rigs = 36cores (72threads) @4.5GHz+... and 5 of them would only need to be switched on for renders, etc....
i have already "acquired" 2x i7-970's on sabertooths, from a school's upgrading (my mate is the head), for ONLY £500.
...the workload spread out over many identical systems in a farm, is faster as there are more BUS lanes for data to travel (???)