Sailboats and Audio

Currently I am in the market for a 40 foot sailboat. The problem is the audio systems are just rehashed car systems. Does anyone out there have any suggestions. You cannot have in-wall on a boat usually without compromising the structural integrity, on-wall is very acceptable. Marine grade (that is water resistant) is probably not necessary because it will be in the cabin, and doubtful whether I will have any speakers in the cockpit. I thought about a 120 volt system but that would require a very large capacity inverter and/or generator system, which is ok.

Can you get the Mark Levinson car audio stuff separately without purchasing a Lexus??

Any suggestions would be greatly appreciated!
Figuratively I am in the same boat as you, albeit with a 36 foot pilothouse trawler that I took delivery on two months ago. The 120 volt system would be fine for shorepower applications, but is too inefficient electrically to use with an inverter. I do feel that with respect to 12 volt systems, you would be advised to check out marinized systems due to humidity considerations (also assume salt water application on a vessel of that size). Looking at 12 volt head units from Kenwood and Jensen now.
It has been a number of years ago, but I found myself in a very similar situation. My solution was inline with yours, though for the passing of years the gear selection was different.

I used on-wall monitors (for all of the reasons that you have already outlined) and attached them with sturdy hinges (with removeable hinge pins so that they were easy to install and remove) on the top of the speakers and thick felt pads on the bottom of the speaker where the rub against the bulkhead. Speaker wire was neatly run with other onboard wire harnesses.

For amplification and sources, I used an integrated unit...the Advent 300 which WAS made in a 12V version (I have seen them a time or two on AG)....and a Nakamichi 550. For the time, the 300 was one of the very few "audiophile" components that was available in 12V. You have more good choices now in 12V, but the idea remains the same.
You should still use outdoor grade speakers in a marine environment because of the high humidity. There are several hi-end(ish) brands available.

I've seen literally dozens of the Levinson car amps on eBay. Can't recall seeing any other ML auto periphenalia though.
Not sure about the audio, but I can help you with a boat. :)

My father just put his 46' Seamaster on the market last week. Drop me an email if you have any interest.

Good luck.
McIntosh has nice car audio systems. you can look there.
Make sure any audio system you put asea isn't on a boat named the SS Minnow.