I was discussing with Gary last night how Kontakt just uses one processor in a dual system yet EXS seemed to easily use two. Well I did some digging and the trick is as soon as you do a new instance of a plugin, then that starts to use the 2nd CPU.
I took a GPO piece I am working on and instead of loading all the strings into one instance I opened one instance per sound. Sure this may seem a wast of resources when you have eight slots but the load on my Dual 1.42 was split into the two processors and reduced by about 20% (if you added them up). I then added an instance of Gold (whose player is somewhat more easy on the cpu) and 4 instances of Opus1 all playing this huge string section and the mac never clipped once. At this point I would have had a couple hundred voices going at the same time and a Space Designer reverb running as well.
Now just putting a KS program in slot 1 will suffice, although I will probably add the Aggressive up/dn to the KS program.