Low end can mean 2 things:
Low RPM power - Treats reed kit, low rpm pipe like a circuit. Stock gears should get you past 30 easy. Maybe even taller gearing to make it more civilized at cruising speeds. It seems like you want this.
Low speed power - either that^ or high rpm power with lower gearing. If you go this route, your bike will accelerate faster, chug more gas, be more fun, be more annoying, and maybe a performance crank. Treats reed kit and the kstar will do this pretty well with a higher rpm pipe. A bigger carb definitely helps too.
I recommend the treats reed kit, circuit pipe, and stock gears. EDIT: oh yeah and your stock crank will be fine with that. (edited)