MacGregorSailors.com

Cabin speakers in the bulkhead at V-berth.
The speaker installation was actually pretty easy. Pulling the wires #%$##%^#!
Cockpit: Sony 5" marine speakers. One is on the starboard side of the steering pedestal below the throttle lever. On the "X" this is mounted in a piece of smoked plexi. (not sure if this would work on a Mac "M")
2nd speaker is under the captain's seat, with the wires spliced by a trailer wire connecter from an auto parts shop.

Receiver / CD player is above the head door. I opted for a normal car stereo, not a marine version. It's been 3 full seasons and no problems.

Hakuna Matata

My set-up is like Dave Mellon's. The swingaway speakers at the companionway work great and stay dry.
I mounted the forward speakers on brackets; one above and forward of the dinette, attached to the compartment
above the mirror, the other on the port side straight accross from the Starboard speaker, attached to the ceiling liner.
The stereo in mounted inside the Starboard compartment above the mirror. I ran separate power wires back to the
fuse panel. I used a Radio Shack antenna splitter hooked up to the VHF antenna. Make sure you get the correct splitter or you can blow out the radio when you transmit on the VHF.