Oh, and ashley9803, 8 GB is the largest RAM stick of which I'm aware.

      And to address luckybears' opening question:  

•   processor cores  -  The more you have, the faster Firefly will render.  HyperThreading will allow you to render twice as many threads as you have processor cores (albeit the virtual threads only run at about 2/3 to 3/4 the speed of the actual physical cores).  So, a core i7 quad will render eight threads, whereas a Q6600 quad will only render four threads.  Firefly maxes out at 32 threads;  you'd need a HyperThreaded dual octal processor pack to hit that limit!
• RAM  -  It's not very expensive now, so if your budget allows, get the max that your motherboard will handle.  Some programs -such as Vue- will reward you with much better preview quality and faster reaction to the controls.
• decent graphics card with some onboard memory  -  An easy goal to meet with today's cards, the benefit in Poser is to be able to preview in OpenGL with hardware shading enabled.  You'll see tiled materials actually tiled -which lets you adjust the tiling scale easily- and you'll see procedurals displayed, with scale/frequency et cetera accounted for.  Again, Vue will make much use of a good graphics card, giving you a preview quality which rivals a draft render.
• extra hard drives  -  Secondary drive to hold your scene files and renders, and a tertiary drive on which to archive content zip files and old scene/render projects.
• mouse jiggler  -  Looks like a flash drive, but it just moves your cursor one pixel every twenty seconds or so;  during renders, it will keep your computer from going to sleep.
• good cooling  -  Remember that you'll be running the processor and memory very hard for extended periods when rendering.

     Since you don't seem to be on a tight budget, You might consider a hex core Xeon processor;  they're HyperThreaded, so you'll be able to render twelve threads.  :)

     12 GB motherboards are quite reasonable now, and will give you plenty of punch (but if they offer 16 GB, so much the better!)  This build would give a lot of bang for your bucks.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5