if you have the option of mechanical brakes, you can get an esc that can handle up to 7s lipo and is actually very sturdy. it is the one i have for my savage with a KB45-8xl on 6s lipo. it does not need a pistix and the best part is, it only costs $28.
it is a 100a esc, but in reality, it handles 85-95a constant. my motor is supposed to be able to draw up to 150a and the hottest the esc has gotten after a 25min hard run is 145F.
http://www.hobbycity.com/hobbycity/s...ies_85-95A_ESC
They say a good mechanic only needs 2 tools - WD40 & Duct tape. If it moves, and its not supposed to, duct tape. If it doesn't move, and its supposed to, WD40.