First, I hope you all have been well and I am glad to see this forum come back on line.
So, I'm thinking of adding a 12" sub under the helm for my '21 Craz. I currently have a 2-8" barrel shaped sub running off JL amp that also powers the other speakers in the boat. The local stereo store says I should do a dedicated amp with 12" sub. That I will get a lot more out of it. They quoted me a 12" JL Audio M7 running off a JL audio 1000w amp. XDM1000. They would build a custom box. Total quote is $4200.

So, my questions:
-This is a bit more than costly than I expected. Will I get that much more punch out of it to justify the $$?
-I have some skills with wood and the basics of setting up a stereo, not an expert, but understand more than average
-Should I consider this myself? If I built a box, do I want sealed or ported. Possibly a prebuilt from Amazon? ( yes, I know I have to waterproof it)

I won't be doing this til spring, so I have plenty of time to hash this out?

As always, Thank you in advance for you thoughts and advice