Don't skimp on the chair. It's something that we do spend a significant amount of time in, and can either make life comfortable or miserable. Like other posters mentioned - make sure there are plenty of ways to adjust it; make sure to check out used office furniture stores (or at least go to see the new ones, find a model you like, and check for it online - Ebay, Craigslist, etc. - to see who is getting rid of a relatively new one).

There's one last thing. Once you get it, you'll have to make sure that it's easy enough to pack up and bring home with you every night - otherwise, you may continuously find it away from your desk!