amp question
 

what is the differance between 2 and 4 ch amps.

i also want to know what kind of amps are the best for giing power to both speakers and a sub. or do you need to separate amps for best quaility?

2 Channels = Fonts or Rears Only
4 Channels = Both Fronts and rears, sometimes you can merge the two rear channels to create 1 sub channel...

A 2 Channel amp will not give you fonts.

Its best to run a class D 1 channel amp for the sub( make sure it is at least 1.5 times the power to your front speakers), and 2 or 4 channel for the front and/or rear speakers, as long as you are not bi-amping your speakers. Are the amps bridgable? Are the amps 2 ohm stable? For example if you wanted to amplify your front speakers(2) you would need a 2channel amp. If you wanted to amplify you front and rear speakers(4) you would need a 4 channel amp. Does this make any sense?

yes, i get the 4 channel for the front and back speakers. but can you than add another 1 channel amp for the sub?

yes, you can run a 4ch and a 1ch at the same time. What headunit are you running? make sure it has 3 sets of at least 4v preouts (front, rear and non fading) if you would still like fader control

Or you get a 3 channel and run the rears off the deck's amp. You don't need that much sound out back anyway. And I'd base your sub amp off of what kinda setup you want, (sealed, ported, BP, etc.) not the other way around. That way you can ensure that you're giving your sub enough juice, or not too much juice.