id get the 660 before a 400... look for a used 07 450 or an older one with the ol mod done to it. the 07 the oil mod was fixed by the factory, older then 07 the oil mod can be done pretty ez. they are good bike. i have beat the dog shit out of mine and its still running like a champ. im thinking of either buying another or getting rid of my banshee and getting a nice mx 450