I had the same dream when I bought my DRZ400SM. Actually, I've been very pleased with the results.
The DRZ was really fun at the track. It is far from the quickest thing on the track, but I had a great time anyway, and with some mods you can get them to go more quickly. In under an hour, I can have it all set up in dirt trim, and go ride the trails. It does both well, at least well enough for me.
I'm not sure what you'll find for $4000, though.
