The problem with building or buying a today's "top of the bill" system is that they age unbelivably fast. They will be 1/2 of the cost in 6 months.
Or twice the power for the same cost.

Only thing Poser needs is a fast multi core CPU, lots of RAM, and a reasonable Graphic card.

 

CPU, RAM, video card in that order.

Drop the video card a stage, Poser does not need it, and double or tripple the RAM.
RAM does not cost an arm and a leg these days.

In your current systen RAM will become the bottleneck.

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!