Amplifier installation question..

I've recently got a hair up my bunghole to upgrade my audio system. After conferring with a few of my audio installer buddies, they seem to think i want to keep my current draw on my 12v system under 40a, which i fully understand.

Yet, there's only so much you can do with audio under 40a. The minimalist system I'm wanting to go for has around 130a draw at its peak.

Now here's my question/idea, let me know if I'm crazy or if it's unreasonable. Since I'll only use the system anywhere near full power for around 1-2 hours a day and have around 1.5 hours where I'll be driving, but not using the system at all, could I add a 200ah deep cycle battery, that is isolated from my 12v system, and run my audio off of it. Then have a 40a 12v to 12v charger topping it off from my cars 12v system? I could also to off the deep cycle when I get home with a battery tender if it is needed.

Again, if I'm being crazy, or it will cause some harm I'm unaware of, please let me know.
Thanks, my prius pimps!

Edit: It's a 2025 prius nightshade