F-150 Supercrew design and build help

I am wanting to do something under the rear seat of my truck. I am wanting to build a SQ system. Unless I raise the rear seat, I'm looking at .70 cf per chamber in a sealed setup. Without raising the seat, this setup would either be up firing our down firing. I like the idea of using 12s to cover more range than 10s. If I raise my rear seat a couple inches, I could possibly fit regular 10s in a forward firing setup. What is the preferred setup as far as subwoofer size as it pertains to volume and sound quality? I've also read that some good quality equipment can be had using brands that are not household names I.e. Fosgate, Kicker, etc. I am not severely budgeted but I'm not hemorrhaging cash either. I will build the system and enclosure myself. Once I figure out, with some help, the subwoofer issue, I'll move on to planning the mids and highs. Any and all opinions are extremely welcome. Thank you in advance