slo, still excellent info for all; couple of his questions
1) Some controllers are better than others because they have superior fet's (look up - has to do with the amps they can distribute).
2) Mid-drive best choice for steep hills and off road; less chance of failure since you can use gears to control rpm and keep it in most efficient range.
3) Most electric motors are most efficient at 80-90% max, but can run fairly well at less speed.
4) 1000w add on system means BBSHD, Cyclone, lectric cycles, lightning rods kit, tangent motors, AFT or others. BBSHD most user friendly.
5) IMO, most important consideration is battery --- can recommend only Luna Cycles or EM3EV and only conditionally.
6) Read all threads on whatever system you select to discover tricks and pitfalls.