I take it that you dont drive or are going very far away for uni because if you're going by car a standard desktop isnt hard to move.
Its not that big a deal to take a desktop to uni. Everyone says get a laptop but for 95% of the time I just used a laptop it stayed on my desk, then I bought a desktop again.
Netbooks wernt available cheaply at the time but they are a good idea I feel, and I have one now.
Certainly around my uni there are loads of computer rooms so its never really worth the effort of taking my laptop in. Occasionaly take my netbook in but
tbh a usb pendrive is all you really need.
I'd say you'd be fine with just a small atx or a matx case, and whatever you want to put in it.