IMO a tablet (while awesome to have) is really not a replacement for a laptop. This is going to depend on your major, of course, as Office-type work will swap over a lot better than, e.g., programming a microcontroller, where the software just isn't available on a tablet.
Moreover, I fully expect that you will want a laptop at college. I can't imagine what I would have done without mine. There's plenty of instances where you're going to want to get work done outside of your dorm, and it will inconvenience yourself (and possibly others) to not be able to do so. Also, keep in mind that if you use it a lot, even a good laptop will probably only last about 3 years, so you may need to buy a second one before you graduate.
This is not to say that you can't benefit from a gaming desktop, either, however. I know when I was doing 3D CAD drawings in '05 I finished well ahead of those on laptops because I had my Geforce 7800GT powered desktop and didn't have to wait for lag when rotating and zooming, etc.
The good news is, I think a $2000 budget is PLENTY to get both a fast desktop and a decent laptop. Personally I would probably split that down the middle--1k will buy you a really nice laptop these days, and certainly a decent gaming desktop. Plus, the desktop can be upgraded when you come across money--like in a summer internship for instance.