I am seriously considering a high-end PC for 3D graphics.  My primary use at present is DS, Reality and LUXRender, but I also have Poser Pro 2012 and will be using that too, in the future.  I know that for Reality/LUX, GPU rendering isn't working very well currently.  I know I want a high-end CPU, and the system I am contemplating will have an Intel i7 Six Core Enhanced processor overclocked to 4.5 Ghz.  I plan to start with 16GB memory, but can upgrade that now or later if needed.

My key question is, does it much matter what graphics card I install?  I want to stay with NVIDEA, but I am wondering if I should go with a Quadro 4000 (3GB) or am I better off going with something in the GeForce line, like the GTX 680?   Or maybe the new GTX 690, which apparently is a dual processor card.

Any thoughts form you experts out there?  Do I wnat to install more RAM or is 16GB enough?  What's the best graphics card for LUX?  For Poser?

Thanks for any help or insights you can give me.

  ~ Russ