shouldn't worry too much about heat and CPU, people make huge deals out of them but basically get a 700+ watt CPU and put a big fat Zalman cooler on the CPU and you'll be okay.  Be sure to get good thermal grease when you install the cooler, often the freebie grease is garbage.  Shouldn't even try to use the Intel cooling fan that comes with the boxed version of the CPU, they are almost always junk.

Poser renders will come in at different speeds depending heavily on render settings.  I would bet a hundred bucks that it's not that simple, because rendering with raytracing on works profoundly differently mathematically than with raytracing off, and I'd expect things like Ambient Occlusion will also affect render time on one processor or another.  I'm not saying this one or that one is faster or better, but just be prepared for unexpected variation between the two brands, that's all.  Intel might whup AMD's butt in low quality renders while AMD might win in max quality renders  (MIGHT, I haven't actually looked at it that hard myself).

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