RE: help me choose a nitro for $400
Those Kyosho buggys are VERY nice. Also the Ofna buggys you mentioned will be much nicer than anything Traxxas has to offer IMO. Pretty much any of the major branded buggys will be great for what you want to do with it. I would definently go that route. I have even seen people put SC bodies on 1/8 buggys with some minor modifications and they look pretty good too! Good luck!