For some reason, I thought yours was a dual core, so part of the upgrade was going to a quad-core (actually, that's what I meant by "having your heart set" - going to quad).
Let's see if I have it right now: 2.0 to 2.2GHz, 256 to 1GB VRAM (similar GPU generation), hi-res to low, no AppleCare > AppleCare. Still seems like most of the difference is the AppleCare, and some performance improvement going to the 2.2.
If you make the trade, you can always sell the machine when you find you need a hi-res screen.

Then, possibly get a refreshed machine next year.