rramsey -
the two fastest (off road) guys I know are riding XR400s. they are uninspiring in stock form, and even un-corked the XR will not hang with a CRF450, YZF/WR450, EXC450, etc in a drag race. however, all those high performing 4 strokes require as much or more maintainance than a CR250.
if you are not married to the idea of riding a red bike, and you want a 2 stroke that behaves better on the trails than the MX bikes, snag a ride on a KDX200-220, or EXC 250-300. their maintainence is th same as any other 2 stroke, with the exception that the big 300 will require fewer top-end rebuilds.
however, a properly jetted, suspended, and uncorked XR400 will go down the trails as fast as anything on the market.
jeremiah