Snow leopard and 64 bit reaper

I'm also interested in 64 bit, if it gives me the following advantages; Better multi core CPU usage, as far as I can see the Reaper only uses one CPU on my imac 2.4 Ghz Intel Core 2 Duo at present. Better Ram usage More stable plug ins , though my set up seems to work at present, the downside of 64bit would be more problems with plug ins.. I've been searching around for info on multi core systems and plug in and FX count and not as yet finding any clear info on the advantages of multi core systems... The bottom line is how much performance can I get out of a reasonably spec iMac system anno 2010? Regards Wade