unlimited as long as you series/parrellel them. You will keep dividing the power, so you will have to determine how much power you need per speaker.
With that said--a 2200 watt 2 channel amp and a 2200 watt 4 channel amp--I am guessing it is not of a high quality and probably doesn't do anywhere near the power it says. What brand is it?
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Who cares What I use? Remember your five "P's" Remember the KISS principle NEVER forget about Mr. Murphy -Be PATIENT!- This is why the car sounds great!