Hardware And Virtual Instruments, What most impacts the performance of virtual instruments Options

[fishbite]

I have a 2 yr old dual processor G4 with 1.25 G RAM, no off-board audio gear. I can't provide the processor speed right now because I'm not at home. I have numerous commercial and free audio unit instruments. However, when I'm working in Digital Performer I find that I can typically only have a couple instruments playing simultaneously. I have to disable tracks such that they aren't playing or "freeze" them (you DP folks will know what I mean). Plus, I often have to twiddle with the latency/sample size or audio playback will break up.

What would have the biggest impact on the ability to play virtual instruments simultaneously - faster processor? more RAM? Should I expect to really only be able to work with one instrument at a time?

I'm looking at getting a new Mac - and yes, I already anticipate problems getting universal binary versions for at least some of the instruments. However, should I go for the fastest processor, biggest RAM machine I can afford? Or what? I welcome any advice.

Thanks,

Seth