Hello Andrew.
A normal bas head has two stages- the preamp stage, where you shape the sound, and the power amplifier stage, where the signal is amplified for the speaker.
JH system has them separate, and that gives you more possibilities. So...
- If you don't use a cabinet at all you don't need the JH power at all
- If you don't have that much money, you can still have the same great sound for the Hose PA, by buying the JH pre and a cheaper power amplifier
First of all you chose the speaker combination, You can use the Big Cab, and the Club cab as stand alone. You can use the Low Cab + High Cab, or Big cab + High Cab or low cab + club cab.
Depending on which combination you use, you chose then the power amplifier, to match the speakers.
For Big Cab you need 500W, for the rest of them you need 250 W each. So if you use two of them, you can use a single 500 W and link them parralel, or a stereo power, and link each one to a channel.Of course, if you use the big cab and hi cab, you can buy a 500 and a 250 power too