Marine amps and stereos are mainly different because the internal boards are coated with a sealant and the faceplate has a better seal. The composite outputs (RCA's) are made of non corrosive metal as well. Amps are basically same principal. Speakers are usually made with polypropelene cones and rubber surrounds. Again, non corrosive metal around the magnet/coil. Most speakers, even non marine are made of polypropelene and rubber now. Back in the day it was more paper cones, which were bad with moisture.

As far as good, I'm a fan of Polk MoMo and JL as my top picks.

I put Polks in the Chris-Craft last year and they sound real good for the money.

Add the sub. Well worth the money. You don't really have to go huge amp and multiple subs. 200 watts to any of the 10" free air subs or EVEN one of those self powered bazooka subs will just give a few more lows to the system and make it sound fuller. Any of the subs can be well hidden also because of the wave length.
The idea behind the sub isn't to have a stripper pole. It's to make the girls want to look for one!

JL Audio make some REALLY nice stuff, but, you PAY for it, I guess its no big deal if you have 200 or 300K tied up in your boat, but, sadly, thats not me! LOL

I have been leaning towards the Polk Audio Marine subs and there 6501 component speakers, I also have heard a lot of good things about the Alpine PDX amps, any thoughts?

Michael

PDX amps are fantastic. I have 2 in my boat. I run the automotive version amps.

JL HD series amps - VERY efficient (no dead battery) regulated power supplies, small foot print, lots of power.
Get the marine versions

Also JL speakers - you want powerful - look no further.

Focal polyglass

x4

We have been pulling out Polk Momo's and putting in Focal CVX 165's awesome speakers.

Most of the speakers out there today have poly cones and you don't have to worry about getting them "wet" like you did in the old days and use marine speakers.

Ditto They rock and the sound is beautiful

NK

I also have Polk momo's in the cockpit with 2, JL13W6's. Cuddy has Eclipse.All on Alpine amps and capaciters. 3 years and it'll still vibrate your eyeball's!