Should I buy an internal gear hub system for my Traitor Luggernaut? The Spacing on the rear is 120mm with horizontal drop outs. I don't want to buy a road bike at this time and would like more freedom on the hills down here in Texas. Going to use this bike for light workouts over the Winter. I've already checked out the Sturmey Archer product offering but would like to know what other options are out there. Any help is appreciated

-Thanks