Simplest iPod Amplification for Sailboat?

Hello all,

This is my first time posting here, so thanks in advance for any help you can give me with what may be an unconventional inquiry.

I have a small sailboat and I am trying to install a simple stereo system. All I really want is 4 speakers to play from an ipod. I plan on cutting some holes and installing 4 waterproof speakers, two outside and two in the cabin. I would rather not use a conventional stereo receiver (deck?) for a few reasons. First, I really don't need CD or AM/FM functions. Second, boat battery life is a constant struggle and I want to minimize power drain. And most importantly, I really don't have any place to mount a receiver because they all need at least 6 or 8 inches of depth. There is only about 3 inches worth of space between the layers of fiberglass in the cabin if I were to mount it anywhere convenient.

Is there some simple amplifier or receiver device that can just amplify from a auxiliary connection (ipod) to the speakers? I could cut a hole and mount it in the cabin if it were shallow enough, or just bolt it somewhere out of sight and run the aux cable to where I keep the iPod. I would wire it up to the circuit panel on the boat so I could turn it on and off even if it were out of reach.

The people I've spoken to so far seem to think I need a real deck of some kind, but I think there should be some simpler fix. Any thoughts? Thanks!