Your electrical can't be too strong (at 12-15V), only too weak. So any alternators or battery upgrades you can afford do it. But big 3 and the heaviest cable you can get are my recommendations.

BTW the Q15 is my all time favorite woofer. So enjoy, and tune lowwww.

If you need some free box designs just post your maximum desired dimensions and I'd be glad to help you there. I do it for a living anyways so I don't mind doing a few for free here and there. You seem like you have done your homework so far; I'd be less inclined to volunteer if you were the typical know-it-all noob

Oh and if you go sealed on the Q15 I'll keeeeeeeeeeeeel you

Smh can't begin to tell you how bad that erks me