Well I took the bird up to the LHS, and they tested the RX by itself with a stand alone battery (no ESC) and sure enough, it seems channels 2-6 are dead. Supplying power to any channel but BAT and THR gives no power to the RX. You can put the battery in BAT and stick a servo on THR and it works, channel 2-6 = nothing.

I'm too scared to plug the new AR6000 I bought into the old ESC for fear it may fry yet another RX. The guy at the hobby store didn't seem too interested in it either. He did try putting the throttle trim all the way down, other than that I'm not sure what else to try on the DX6 to try and arm the ESC (considering one day it worked, the next nothing).