I'll be installing four 6x9's and two 12" subs in the Superboat. The 6x9's will be in the cockpit area. What's a decent nominal wattage each? What about a four channel amp around 40 or 50w nominal?

match it up with the rated power of the speakers.

I have roughly 2000 Watts going directly into my cockpit, feeding 8 6.5s and 2 10" sealed woofers. Its sounds like a MUCH more involved system. Follow what Will posted above. Power your speakers by the amps made by the manufacturer. JL Audio matches this up very well as does MB Quart. Also, go for at least 2 way, maybe even 3 way 6x9s, if you are that bent on 6x9s. Rounds look better in boats anyhow, and those 6x9s combined with two 12"s are going to give you probably more base than you want.

The vast majority of the systems that I do are only about 40 watts each speaker and then 200 or so watts to the subs. I have used a number of 5 and 6 channel amps and they seem to perform very well.

That being said you did not tell us how loud you want it to play, or what kind of music you listen to and so on. How important is it that the system can run off the battery and so on.

Jon

Put in more power than the guy you tie up with... don't want his stereo being louder than yours!!!

Feel free to use if this helps:

Jezz Brian that shure is purdy

I would recommend a 200-400 (50-100 per channel)watt 4 channel amp for the mids and highs then an amp to match with the ohms and power of the sub(s). Or to keep it with one amp run a nice 5channel amp with the set up 1 amp 2 rcas to the amp solo power and grounds and easier to stuff/hide out of site.

Jon, thank you very much for your advice during the planning/build. It all payed off nicely.

Power Diagram:

I have 4 Optimas wired as two logical batteries (parallel), and a 25fd Digital Capacitor with digital voltage readout. The dash switch controls stereo power. The hidden toggle switch allows me to keep the amps off when I chose so I can just run the stereo with two cabin speakers at night. The 200 Amp CB is close enough to the battery that I can use at this point, the charging/discharging resistor to perform such to the capacitor for maintenance.