I'll let some of the other guys speak for the motor and lipo's..
but I'm planning on buying a 125b tommorow actually, but if you're not going to run this truck until next spring/summer, I'd wait on buying the controller until you're ready to run.. I'm not sure when the Mamba Monster Max will be available, but i'm thinking before next summer? that controller should be the best controller you can buy.
also hold on the lipo's. the technology is advancing so fast, if you set your mind on a type of charger/cells, by the time you go to run the truck, there will undoubtably be better options available, and prices will have dropped as well.

also, you said roughly 16-18cell lipo's? do you mean lipo cells equivilant to 16-18 sub-c nimh's?