Thanks @MindseyeDrums! Sorry I didn't answer, but I don't check these forums that often. I'm on SL now (of course) and my Macbook is a 2.4Ghz with 4GB of RAM... but anyway, I'm blowing away the CPU (passing 80% much of the time now) so... not sure what to tell you. More is more. Guitar Rig is a CPU hog, ESPECIALLY the amp models... you really have to watch your CPU usage carefully and see what causes spikes.