choosing a system on a budget

Well,  I dont have any experience in instaling boat systems, but from what I hear it isn't that much different besides the fact that you have to deal with water.  There are a few things that would be helpful for ust to know in order to help you more though.  Will the upper deck speakers be subject to direct water contact?  If so you have to purchase some sort of marine speakers that are waterproof.

For your lower deck speakers (asuming they won't get wet) you can either get some better 6x9's or you could go with a component system if you realy want to sound good.  Whatever you do I would suggest that you see if you can create some sort of "box" for the speakers (better bass).  If there isn't room for a wooden one I have heard of people using expanding foam to seal a narrow area between to surfaces (have no idea what kind of boat you have).

As for a head unit you should be able to pick up a decent one that has CD-RW/MP3 capability and a remote for like $150  (I know a couple of JVC's arsenal series are in that category).  Just make sure it has a decent amplifier and enough adjustments to play around with.

On the sub issue, that is where things get complicated.  I would say to find a place for it below deck, because you will get the most pleasure out of it that way.  If you are only going to have 1 sub, I would say get a 12".  You budjet wil determine just how nice of one you will get though, but expect about hafl you system cost to be in the sub, amp wires, and box.

Personally I would upgrade the 6x9's outside, get some nice 6x9s for inside, a decent head unit, and a 4 channel amp.  This will probably put you in the $500-600 range.  Then you can see how it sounds and  decide wheather or not you need a sub or not.  Those 6x9's can put out some real bass when on an amp.

my 2cents

Heres a system I reccomend:

Deck: Alpine CDM-9823 cd player

Deck speakers: Infinity Kappa Marine 692M coaxials

Below deck speakers:  Alpine S SPS171A component set

4 channel amp: Hifonics Warrior Eagle

The Alpine deck has two sets of preamp outputs and has a nice sound for its low price. The Infinity Kappa marine speakers would be a good choice for your deck speakers since they will be exposed to the elements, and Infnitys Kappa speakers always sound nice. For below deck speakers I would look at the Alpine Type S 6.5" components because of their ability to play low frequencys better then the average lower end component set and they are very effecient also. For you amp I would use something like the Hifonics Warrior Eagle amp to power the component set and large coaxials. Your total comes out to about $700 dollars for everything including an amp wiring kit and speaker wire. This is more then you wanted to spend but I think you would be very happy with the way it sounds, and if you want to buy something that will last out at sea I would consider this gear. One last thing, you might also want to look at MB Quarts marine speakers if they are sold near you instead of the Kappas. And an alternative amp for your speakers might be a Planet Audio one if they are also sold anywhere near where you live (they would be a good choice since they come with a 5 year warranty, perfect incase they get damaged out at sea).

Thanks for the reply. As for some answers to your questions,,yes the upper deck speakers could see water splashed on them. The ones in there now are marine grade. I really dont know if they actually are still good, cuz the stereo putting the juice to them is so poor.. Perhaps, they might be ok still. Off hand I dont remember the brand, and cannot check now, cuz I am at work.  The ones down below are mounted to the furthest forward panel, facing towards the rear of the boat. They are both in fact mounted on the same panel, which is actually a sealed box behind it. It squares off the tip of the boat from the inside, approx , a 3 foot wide box in the front that forms a triangle on the inside. Should the backside of this triangle be padded or foamed somehow, or is  fiberglass box ok? Is it ok for both speakers to be mounted in same box, per say? The rear speakers are  are only face mounted to the base of the rear bench seat. Again, it is a huge 3 sided fiberglass box, and behind that box is a wide open engine compartment. Should those speakers be boxed in from behind too?Individually I assume. And how big a box, is wood ok? Pad it or not? As for the head unit and amp, I suppose I could start by buying just those two pieces first, and see what it sounds like. Can you recommend more specifically a good match, that will work, and maybe handle a sub  add-on later? Sorry for all the questions, but I am trying to learn .My skills are mechanical in nature, certainly not in electronics. This would be a full time job for me just trying to keep up with all thats involved here in this world of electronics.  thanks again Rich. 

1. I would put a box behind the 6x9s and below deck speakers if they are exposed from behind to the engine compartment. You could add some polyfill (or as you refer to padding but im not sure if this is what you mean) to the boxes (stuff about 3/4 of the box probobly).

2. Yes, you could start off by just buying part of the equipment. After you get home from work could you maybe post the brand and modle if possible of the current speakers you have (if they are old and damaged you should buy new speakers and a cd player first instead of an amp and cd player first). The upgrae after new speakers or an external amp would probobly be an amp and sub combo. The Hifonics amp I reccomened has preamp outptus that you can send to a sub amp in the future so you should be fine. If you buy another amp you can buy always buy an external crossover which would take the two preamp outputs from the cd player and seperate them into three (one output for the front channels on an amp, one for the rear inputs on an amp, and one for the sub inputs on the sub amp).

If you dont feel like you can handle the install you should check into having a local car audio specialist do it for you. If you are a DIY kind of person it shouln't be too hard and if you order from crutchfield or a local shop they should give you tech support when ever you need it.

I can make the boxes under the rear seat any size I need to, really.  Its just a matter of closing in the missing back side of the box as much as I need to. Do these boxes get filled with poly foam as well? And as for the speakers down below already in a triangle shaped box, you are telling me to fill up that cavity with some polyfoam as well if I understand correctly. As for the type of speakers, I will find out what they are tonight and post them. I know that they are two different brands, above and below. Its hard to think that  the speakers are shot from being blown out, thats for sure. To give you an idea of what I have, its not even a cd player. The stereo is factory, and the previous boat owner swapped out the speakers for these in there now.  The boat has been completely gone through,and I just finished  the re-power, and am now just turning my attention to some real sounding music in this ride  .

 Has anybody ordered from these guys.. http://www.onlinecarstereo.com/CarAudio/ProductDetail.aspx?Productid=13611. They have the alpine you spoke of, but one model better, the alpine  cda 9825, and its cheaper. Also the speakers are here to that was recommended, the alpine type ssps171a, and they are $60 dollars cheaper. Please take a look and tell me what you think.