Audio Systems: Speaker Wiring, 1000 watt amp, sony marine

Question
My question is actually for a boat but the wiring should be the same. I have a Sony marine head unit which functions the same as a car HU and I have a Sony 1000 Watt amp from Wal Mart. I have 4 6x9's on the tower, (4) 6 1/2s in the rear of the boat and 2 more 6x9's in the front of the boat. The Amp is a 4 channel and I currently have everything wired to the first two channels, and the tower speakers wired to the last two channels and they are bridged so that they can get the loudest. I have all four of the tower speakers wired positive to positive and negative to negative and one wire running to the amp (I guess this would be a series?) I have the remaining speakers running straight into the channels, with the (2) front 6x9's tieng into the first channel as well. The tower speakers put out way more bass than they can handle and they distort if they are turned up too loud even when I have the bass turned all the way down on the H/U. Any ideas as to how I can fix this or some suggestions on my amateur wiring job would be really appreciated.
Thank You,
Darren S

Answer
I am not sure from your description what you have for the wiring scheme but it appears you have ignored impedance matching - which is important.

Go to this crutchfield site where they have many wiring schemes that will teach you how to connect them for correct impedance matching.  You may have to acquire another amplifier for independent drive since you seem to have big differences of sensitivity among the speakers.

http://www.crutchfield.com/S-de0wm4ZH6c4/learn/learningcenter/car/subwoofers_wir...

These refer to subwoofers, but it applies to full range speakers as follows.

Then send me a follow-up if you need further discussion.