As a SonDORS owner, I have been following the "mods" posts. The 25A controller will kill your battery in a big hurry. Go for the 20A version for some extra zip. The real answer is a bigger battery and motor if you really want to do hills. I think there is a 500w motor out there was well to fit fat bike wheels.
AKAIK Europeans get the 250w motors. Sadly I dont know how to tell them all apart by looks.
-SP