Supra diffs seem to be really strong, the TRD versions are mega as that is what 8 sec and some 7sec cars are running on. Might cost an arm and a leg to sort though.

I can see why you are against 3k for 9" diff but if bought 2nd hand its still worth the same at resale time and all the hardware that goes with it, instead of investing in modified parts where there is more risk of losing resale value.