building a new system

I am looking at adding a decent sound system to my boat. I just upgraded the 6 interior speakers from stock to DB650s. I want to add tower speakers/amps but don't want to go too crazy. I was thinking a pair or two of the Pro-60s from wet sounds based on my research. Not sure about the amps yet.
I want to do the project myself as I am pretty good working on things and feel like I could save some money. Unfortunately I am not real experienced in the sound arena and wondered if anyone new a good place to start for advice on what components to get (mainly amps and sub). Do any of the companies help you with wiring diagrams based on specs etc. any information would be appreciated. Thanks

whatever you do install is key

power the subs with enough power (if you have 2 300 watt RMS subs, get a good 600 watt RMS amp to power them). Also make sure you build the box for the sub to the correct specs, or throw the T/S parameaters into a box calc program to turn out a box with a real nice rolloff for good overall sound.