I built a dual processor E5 2630.  65g ram and ssd drives.  Poser runs fast.  It will use up to two 8core cpu's so if you have the money, more is better. 

Remember that more cores and more ghz speed is what makes it render faster. 

I gave a lot of serious consideration to the top of the line I7.  The dual E5's were almost the same price but the neat thing is that next year if I want to replace the cpu's with a couple of 8 core and faster ghz, I can do it.  I don't think the I7 is going to be upgradeable in any significant way in the near future. 

So after talking to SM and researching, and making sure you don't bottleneck your system with inadequate RAM or HD speed, ... it comes down to a simple equation.  Cores x ghz. 

The top of the line I7 is 6 cores x 3.2ghz.  = 19.2

The dual system I built is 12 cores x 2.4ghz = 28.8 which is just slightly faster at about the same price.

If I wanted to go nuts on spending money (the E5 2630 is about $650) I'd go with two of the 8 core 3.3ghz and get 52.8 for a total speed which should more than double the I7, but you're looking at over $2k per cpu.  So there is a price/performance consideration to keep in mind.