Not much, as it's the CPU that does the horsepower.

RAM is used to hold the info for things like displacement, textures etc
if there isn't enough RAM, it's "swapped" to the hard drive, which is slower to work than the RAM.

Very rarely will any of my scenes go over 4 gigs, usually only when there's a bug!
Some scenes though are extremely complex and I have used 6 gigs but it's very rare

however...more RAM = you don'tneed to worry about having to compress jpg files for poser characters etc, for better optimization ;)

this one was the only one I think that really hammered my RAM, lol (I have 8 gigs)
http://www.renderosity.com/mod/gallery/index.php?image_id=1755936

I wouldn't worry about more RAM unless you ARE hitting RAM limits, you always assume the operating system takes 500 megs of RAM, to 1 gig (currently that is on these kind of systems)
so if you have 6 gigs, and Vue uses 5 gigs a lot, well, more RAM would be helpful
:)

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