Stereo upgrade requiring more batteries

[PD3]

i would like to upgrade our current two speaker system we have in our select 200 with stock clarion head unit to a either a 4 speakers with 1 subwoofer system (2 in the bow, two in by the consoles and subwoofer under helm console) or to 6 speakers with 2 subwoofers. for the first option maybe a 6 channel amp (4 channels for the mids/high speakers with the other 2 channels bridged for the subwoofer) or if i go with 6 speakers with dual subs than one 6 channel amp for all 6 speakers and another amp dedicated to the subs. right now i we only have 1 battery with a perko on/off switch. i would like to keep the perko switch if possible and add the a selector switch to it as well the ability to charge both batteries simultaneously. right now i am having a hard time figuring out which batteries i should go with. pretty much set on JL Audio marine series speakers/amps/subs. if i go with the 4 speaker setup the the possibly looking at a 600 watt amp to power everything. if i go with the other setup then probably about 1100 watts for both amps total power.

right now i'm pretty clueless on choosing the correct size/brand batteries. i think im correct in wanting to go with deep cycle gel batteries for extended run time. we typically like to anchor up and relax at sandbars or in the ocean and swim. i dont want to go crazy as always there is a total budget for this project $1000-$1500 which already makes me think that the 6 speaker with dual subs is out of the question. our boat has a mercruiser 5.0L MPI engine in it as well. will i have any issues with the stock alternator charging these deep cycle batteries, meaning will it be necessary to upgrade that as well? also i have read on other posts people complaining that when combining their batteries into one large one that both batteries fight with each other effectivley drain each other. by adding the selector switch will that resolve that issue? please feel free to provide any tips/ideas/recommendations for this. i know a guy who i need to convince to assist me with this project. he is an electrician. i havent spoke with him yet as i want to understand everything first and be able to describe and order all parts to speed up this project.

i look forward to your responses.....

 

[HIFI]

I am willing to help with parts of your questions . . . .

The best systems I have heard have strategically placed multiple Sub Woofers. Almost always two Subs fore/aft will sound better than one rich playing sub. It is hard to contain the lower parts of music. The Bass, including Sub Bass, is the “body” of the music. Get it right first.

DEEP CYCLE BATTERY/S

 

[PD3]

How can find out how many CCA i will need for my 5.0L MPI mercruiser? i have read that when going with deep cycle batteries that i should account for 20% more than a typical starter battery. another thing i need to figure out is battery placement. right now my current battery is underneath the seat on the right side of this photo.
http://i48.tinypic.com/35bhxeb.jpg

would i be better keeping the batteries close together and sticking both underneath this seat (if both deep cycle's fit) or should i distribute the weight and put one under the seat and put the other on the other side of the engine?

i agree with your statement just not sure how i would be able to put a subwoofer in the front bow of the boat, space is tight up there, plus i am planning on putting 2 regular speakers up there as well. i will have to investigate further as to what i can do in the bow.