Obviously you've gotta look at Philip Glass's stuff......"Metamorphosis" is a six-part piano work. And the song "Opening" off Glassworks is a f*ckin masterpiece.
Well... I have liked some of the stuff I have heard, but I have also found some truly amazing stuff which is what I was looking for... I am listening to Charles Mingus - Mingus Plays Piano, which I found quite randomly, but it sounds good. I should probably check out some more piano Jazz stuff.