Here's an alternative you might want to consider; a digitizer. It's a combination monitor/graphics tablet, so you draw directly onto the screen instead of using a mouse, tweaking pots and faders directly, and drawing sequencing directly.

I got a Wacom DTI-520 last week; 15 inch LCD, cost $1650 australian, but wow is it fun to use. I have a ReMOTE 25, but think I'm going to sell it now; it's too much of an abstraction to map real pots to pots on the screen when you could be manipulating them directly.

The only downside is that you can't manipulate more than one pot or fader at a time....small price to pay for moving your PC into "almost feels like hardware" territory IMO.