I haven't had a lick of trouble with P5 and I have a P4 1.9 ghz with 256 megs of ram. I haven't tried to render any large scenes with lots of characters yet though, (2 Vickys and a Mike fully clothed is probably the most) and I don't use a lot of super hi rez textures, but still 256 megs of ram has worked fine so far.