Relays to switch b/n head power and amp power

So I have a boat and am putting in an amp, speakers and subwoofer. I am upgrading from the stock system of plain jane head unit and two regular speakers.
The amplifier is 5 way, with 4 regular channels and one subwoofer channel.

My goal is to use a switch, so I can go back and forth between the head unit powering the speakers (low power) and the amplifier for high power.

I want to install some 4PDT relays on the output side of the head unit, and also the amplifier side. The relays are controlled by a SPDT switch that gets its power from the head unit amp turn on lead. It's a break before make switch with center off. I chose $PDT relays so I can switch all the audio wires on or off, the positive and the negative sides

The switch would give coil power to one set of relays NC contacts, and then when switched, this would happen on the other set of relays.
What I do not want, is to burn up my amplifier. I plan of switching between the head power and amplifier power slowly so it allows time for the amplifier to power down.
I am pretty certain this will work, I want to make sure there is no chance of damaging the amplifier.Oh the amplifier gets the audio signal from the head unit RCA outputs.

Does anyone see how I might hurt the amplifier in doing this?

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129 Flowers Lane

Hi scott.
I am new here, but also have a boat.
I was wondering why you are going this route? Is it because you want to use the stereo without the engine running for long periods? If so, why not add an rv battery with an isolator?
If you want to power down the amp, you could put a 2$ switch on the blue power lead, and then the same switches on the speaker leads from the deck. Run 2 sets of speaker wires to the 4 main speakers, one set from the amp, and one set switched from the deck.
Turn off the amps and turn on the deck leads and there you go.

am I way off base? lol.
Corey.

I to am wondering why you are doing this. If it's for reserve capacity then golf cart batteries are your friend, get a pair with an isolator and you can run the sucker all day long.

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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Thanks, and yes this is to save power, don't have room for golf cart batteries although I wish I did. I do have a battery gauge and if I see it getting low, I'll just crank an engine until it comes up. I have three batteries now, one for each engine, and a large 29 group house battery that power all electronics.
I do want to add a second house battery but have not found room to do it.
Maybe I am making this too complicated on myself, but I do like the idea of selectable amplification options, just don't want to hurt the amp.

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129 Flowers Lane