BigBobT:
You sure came to the right place to get a lot of advice on a bike! And, guess what? I'll give you some more!
I too live in Michigan, just south of you guys, in the Grand Rapids area.
I started back riding on an XR250, and the bike certainly handled tight trail, once I put a few hundred dollars into it (or more!). I still think it's a pretty good bike, but once you start getting at least semi-serious, the forks deflect easy, the shock heats up and goes away, the power isn't there....
I thought an XR400 might be the next answer. During the test ride, I kept having to look at the numbers on the seat to make sure it wasn't a 250. I didn't feel any different, maybe a little more power....my modified 250 felt it was putting the same as a stock 400.
I understand about "it's my turn" for a new bike! It's YOUR money buying the bike, why not!!??
All that said, I don't think you'd go wrong with the KTM450. Yeah it costs more, but you won't have to buy anything else for it. The components are first-rate, and the motor has proven reliable.
If you don't mind going used, I know where you can get a 400 with super-redone suspension. PM back if interested.
Also check out the Michigan Trail Riders area under the Regional Chapter/Eastern section on this site. You'll find a bunch of Michiganders setting up rides there, and more than a few of them ride orange!