If you are looking for a good 4 stroke, i would say a LTR450 would be a good choice. Ive ridden several of them before and they ride very nice, plus you can pick one up for relatively cheap. (used)
Also, there are a few mods for the LTR450 that can really give you performance if you ever wanted it.... (Yoshimura Cherrybomb, Pipe.. etc.)
Performance can also help on the trails, even if you arent interested in racing.