You would never 'need' hydroboost on an larger brake caliper setup. Think about it, small piston area (stock master cylinder) versus big piston area (pistons in the caliper) now you make it an even larger surface area with oversize/multiple piston setups. Force = pressure x area. Now in essence, it should take less braking force at the pedal to do the same amount of work at the wheels.

Larger rotors also play into your braking efficiency, the larger, the more efficient. Think of it as leverage, are you going to turn a bolt more easily with a 6inch ratchet or with a 2foot snipe on the end. The same goes for stopping power on brakes, the farther the calipers are located from the center of the wheel (the nut) the more rotating force that can be absorbed. Of course this is limited with rim size for most 'heavy duty' trucks. This is one reason hd's have hydroboost, another is to deal with stopping extra loads that may be added, with the higher line pressure.

On half tons there is no need for hydroboost IMO. If you are towing that often with heavy enough loads that your experiencing brake problems, you should have bought an hd. Stick with the vac boosted setup, and get bigger discs, and/or calipers and you will stop great!

 

SSBC now has a 15" rotor with their 6 piston kit. not sure if it is available stand alone though....