Instead of waiting for the diff to strip out again, just shim it. Shim the new front one you threw in, and the rear one now preventatively.
I wouldn't go overboard with the 540 motor. Stick to less than 4000kv. Just make sure you can find some batteries that'll be able to keep up with the motor combo, that being 35c or higher, to be safe. I'd say 40c-50c packs, realistically though.