I don't know anything about Traxxas, not common in NZ, but Tamiya do some great cars now that are very tunable (is that a word?).
IMHO the AE and Losi cars are no good for bashing. I own a B4, and when i'm using it OFF the track, I always end up breaking stuff.
The Tamiya DF-03 is a good 4wd buggy. Cheap in it's basic form, but tons of hop-ups, and it can handle a fair bit of power. The DB-01 is the next "level" up in Tamiya, but not really necessary for bashing.