O'donnell and Mugen do not need upgrades... mater of fact, when i ran HotBodies, mine were box stock with the exception of aluminum servo horn and won many races with them that way.... i was faster with the stock buggy versus one with all the up-grades
i say look at odonnell, they are extremely nice and last forever, parts are cheap if you even break a part... i have 6-8 gallons on the team buggy and havent replaced one part except a couple hinge pins that slightly bent. the SG buggy is even nicer and im enjoying it alot, very fun and easy to drive