A couple of weeks ago I was pricing Quad-Opteron systems (up to 64 Bulldozer cores).
Now I notice that the Multi CPU PassMark is given for them. http://www.cpubenchmark.net/multi_cpu.html
I don't know how this compares to a Xeon solution, as not every chess program will support 64 cores, and the tree-splitting may suffer in any case.
In any event, the Quad Opteron 6272 in a SuperMicro 1042 can be decently configured (other merchants also available, and different motherboards are possible too) at around $5-6K [with 64GB of memory].
