9xl on 4s lipo

Ive been reading a lot and i think ive narrowed my choices down, im thinking a 9xl with a TrueRc 4s2p 8000 mah pack....would the 9xl be a good choice? Its only for general bashing, no racing, how will the 9xl on 4s compare to the stock K4.6?

Also, im thinking of running the mm with a ubec, would it be worth going to the mmm or will the mm handle bashing ok on 4s

What gearing would anyone recommend (im using the FLM forward tranny kit)

By the way, this forum is great.