i would personally recommend a YFZ 450, but really a raptor 350 wouldnt be a bad choice either.

i do have a friend that is a bear of a guy that has one of those 660's, he does fine with it, and most 450's keep up pretty good, the 660 just has more top end, but i would say for you its not worth it because of the weight increase of the 660.

and if your going for a 400, honda ex's are suppose to be pretty reliable