Does anyone have an opinion re the following: I want to install a car stereo in the boat and drive three (3) sets of speakers, a total of six speakers. One pair outside in the cockpit and two pair inside down below. The decks/receivers all seem to only have output leads for only two sets of speakers, i.e. front and rear. Can I just double up the two sets inside speakers without running into an impedance problem? (I realize that I would only have the ability to fade between inside and outside and not between the in indoor four) Is it just a matter of volume or is the sound quality actually effected? If it is just an issue of power, then could I use an amplifier to boost the power back up? The deck is 100 watts, 25 watts for each speaker lead. The speaker literature states that they are usable with any 4 to 8 Ohm receiver. Paul