in a perfect world you'd like to have each driver to have its own dedicated channel, eg. 5 channels in a system that has 2 fronts, 2 rears & 1 sub.

the majority of people, including me, wouldnt bother amping their rears, so thats minus 2 channels.

so lets say you want 3 channels to power a basic system consisting of fronts + sub, you could:

1. get a 2 channel + a monobloc
2. get a 4 channel and use channels 1+2 for the speakers, and bridge (combine) channels 3+4 for your sub.
3. get a single 5 or 6 or 100 channel amp to run everything, but i wouldnt do this. plus theres no 100 channel amps out there.

if people have a monobloc id assume they have another amp for their speakers too. no magical synchronization goin on

u dont NEED 1 or 2 amps. just depends on your budget i guess. depends on the voice coils of your sub too..