How useful a bunch of cpu cores can be is dependent on the software. If it's not written to be hyper threaded, not to be confused with multiprocessing, having bunch of cpu cores won't do you a thing.
You also need to be clear on two aspects; server vs workstation hardware and server vs workstation software.
You want the best hardware you can get. Rendering needs tons of memory, in addition to cpus, so whatever the mainboard supports maximum is what you need to have in the hardware.
Then you have to consider what OS is supported by the software. For example Bryce is only supported on workstation OS not server OS
You will note where it says in 2006 it "support for dual-processor systems as well as hyper-threading". That is pretty lame considering server hardware has up to 8 cpu's average with many cores for each. So server hardware isn't what you want for this software
Point here is start with the software you want to run requirements and built from there not the other way around.