AB class amps
Class A, B, and AB amps have no place on a motorcycle because of the limited amount of charging system output available to accessories. Since about 1998 the charging systems on these bikes, roughly 1/2 of rated output is utilized by the bike's "STOCK" electrical systems so that doesn't leave much more for accessories. Although this is starting to improve with HD putting LED headlamps, passing lamps, running lamps, turn signals, etc. on these newer bikes.
For example on a 12 FLHTK the rated output is 55A (i believe that's correct) of which at least 1/2 of that is used by the bike at any given time. So that leaves you about 20A (you should play it safe and not tax your charging system by assuming 22.5A) to play with. Everything you do electrical-wise has an effect on this 20A so you should certainly pay attention to what you're putting on your bikes.
Class A, B, AB amps are current hogs. They draw lots of current and produce lots of heat and you're not going to find many (if any) that will fit inside the fairing.
Class D, G, H is where you want to be with motorcycle amplifier components. Very little current draw because of the way their power supplies are used in relation to their output transistors and very little heat as an added extra.
Booster Rail Technology (Rockford Fosgate) is another viable option with low current draw and heat.



