Hey everyone:
Ok, so here's the update:
I bought a reg and computer, taking the great advice I got from this thread into account. I wound up buying a Scubapro MK16/S550 with an R380 octopus. Everything being equal, I didn't really have any forseeable need for the extra ports that the MK25 offered, plus it saved me a few dollars that I can put into, say, a BCD. Bought at an LDS to get the warranty, which will hopefully save me some dollars in parts later on in life.
And I picked up a computer (a Suunto Cobra) while I was there. From everything I've heard and seen, the combination should work really well.
I'll get the chance to dive both next weekend. Thanks everyone for your help! (And I'll probably post soon on the BCD forum for advice there as well!)