If you look into upgarding right now you can get a premium for your 16" rims because people want then fo snow tires.  You could probably get $400 for  them.  I like 17" personally because you don't need spacers, but look at your options you might be able to buy the rims individually and the tires in pairs a lot cheaper than buying them from one person, also check craigslist.
Hope this helps!   
