Rikki, yes the best approach is to have all of the 500mb wavetable loaded given it needs to respond very quickly to program changes (voice changes) within each style or midi file. You don't want any delays due to this. It wouldn't slow down the computer but it certainly will consume all the memory of your laptop. If program changes were not required you could then setup suitable synths to stream from the hard drive with very little of each instrument loaded to memory. Synths which designed to stream from the HD include Kontakt, Halion and GigaStudio.

That's why I compromised and only replaced those instruments that I needed in sYnerGi GS. This kept the size to 128mb.

So if you want to successfully do it the way I have then you need memory closer to 2GB. Again it dosen't slow the computer down. The thing that is hard on the processor is a high quality reverb. Effects can get the audio to break up. Ordinary effects like you find in Yamaha keyboards would not even be noticed by today's high speed computers. I use moderate to high quality effects - it makes a big difference in the quality of the audio output.