Scott, one hears alot about reliability of PCs and Windows XP.....but not to worry. Performers in high places use them all the time: http://www.daviddas.com/
And many others.
If you setup and run your system like I do you would find the PC/Windows XP as reliable if not more so than any hardware based system. I have 2 computers. One of my computers is for general purpose and all editing and the other is used solely for performances (no editing, no online stuff, tweak for optimum multimedia/music use, etc.). I have never had a failure during performances. The only time there are difficulties is when installing new software. Once you get the new software up and running the reliability is as good as ever. So ..... not to worry.
If you look at my system you can do layering, splitting, etc. for your melody or lead voices. I use a separate synth for this purpose and usually of much higher quality. I use Kontakt and very high quality virtual instruments. I set it up on a per channel basis, e.g.,
1 Jazz Organ
8 Jazz Guitar
I usually set these up to fit a genre of music, say jazz, etc. and will load up a different multi instrument for say country music. It works for me. I switch channels from my Roland A37 with the press of 2 buttons.....fast and easy. In future, once Kontakt will beable to accept program change numbers, I will switch over to this approach, i.e., change instruments by sending program change number from my controller keyboard. Now there are many variations on this theme and that is what is good about this....you find your own best way.
[This message has been edited by Frank L. Rosenthal (edited 06-24-2005).]