If I were you, I'd join a few of the car audio Facebook groups and see if you can find a local custom box builder to you. A low end, low power sub will sound better in an enclosure built to spec compared to a $1000 woofer in a cheap, mass produced box that has the wrong specs for the speaker.
I also think that you'd be better off with one single quality sub (Sundown, Wolfram, Soundqubed, even Skar's upper lines come to mind). A +/- 1200wrms sub can be had for a decent price, and if you can find somebody who knows what they're doing to make you a ported box, it should sound REALLY good. You also might go to them for recommendations on what equipment to buy, because, chances are they've been around the block or two when it comes to car audio and can point you in the right direction as far as your needs and wants goes.
