Bill,
I use the Tyros2 for multitrack recordings.
My PC runs CubaseSX3 through a professional (simple, but fit for purpose) soundcard : M-Audio Firewire Audiophile.

Because SX has no limitations in the number of tracks, I first start recording the drums on one stereo track.
The next track e.g. the bass, the next, ACC1 etc.

You don't need a higher polyphony at all, because you record audio on each track !

It's a piece of cake to create fantastic songs with just one kb and SX.