How much RAM for our VPS?
 

I was wondering if I could get some estimations on how much RAM to shoot for when looking for a VPS? At peak times have about 50-60 members online concurrently with the addition of anywhere between 200 -300 guests that can browse threads in certain sections (as well as forumdisplays for the whole site) but not post. We're also growing a little every day so we'd like to have some extra room to expand of course. We run a moderate amount of plugs/modifications (maybe 10-15). Does anybody know what we should shoot for approximately?

Thanks