I have basically the same set up (except 8 gb ram and only one 8800 gtx video card) and it works fabulously with rendering (in Vue 6 Inf 64 bit) being about 800% faster rendering than my elderly 4800+ and dual opteron 246.  I guess to really see the value in Poser we will have to wait for the 64 bit version. 

The biggest change though was getting a 30" dell monitor, I really cannot recommend this enough, it makes such a mammoth difference to making the images (especially once your eyesight starts to play up as you leave your thirties :) )

I know what you mean about storage space.  I keep all my .pzz's and .Vue files and I have in total about 8.2 tb of storage over all my computers and including a couple of NAS drives and I am running short already.

"I am extraordinarily patient, provided I get my own way in the end" - Margaret Thatcher 1989