Thanks, everybody, for all the replies!
There are good arguments both ways, and I guess I won't really know what I want to do until I take a new V6 for a test drive.
One thing that's to my advantage is time. I currently have a few cars that are all drivable so I don't need to run out and buy another car just to have transportation. I've been without a Mustang longer than I wanted to be so I've got the bug to get another... but I can wait as long as I want for now 'till I decide what I really want to do.
I haven't ruled out waiting another year or two 'till I can afford a 5.0 either... which is what I'm leaning towards right now.