If your projects are approaching your RAM capacity, then more RAM improves speed.  Where this "event horizon" occurs varies greatly, depending on the user's work habits.

     Most users would never top out a 4 GB machine, but there will be some whose niche interests push harder.  I tend to make complex scenes and render at large pixel dimensions using a lot of resource-heavy material effects (nods to msg24-7).  I have seen Cameron pull just over 48 GB during IDL precalc.  I frequently exceed 16 GB, but only rarely surpass 24 GB.

BB, do you recall where you got the bar graph CPU/RAM sidebar widget?  I have one that looks very similar, but can only display four cores.

edit:  Argh!  cross posted by BB whilst I was composing my thoughts...

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