I don't know how much this is relevant to you but I have a crew cab nissan frontier. Just last week I had a shop build a box for me. My rear seats are like a 70/30 split. 95% of the time it's just me or me/gf in the truck...I rarely have passengers in the back. I sacrificed the 30 split (drivers side) and just folded the seat up. My local shop built a ported box in that area and it came out great...just a little bit under 2 cubic feet. If I ever need the seat back for a passenger, I can just remove the box (put it in the bed or in the garage) and then fold the seat back down. This way you can choose any sub you want and still keep your seat when you need it. Remember you still have that other 70 split for the 3rd and 4th person...the 5th passenger is when you'll need to remove the box. I'm glad I sacrificed that little space because I knew I wouldn't be happy with the shallow mount subs that can fit under my seats. The only thing that scares me is that it's visible if someone looks through the window from the front passengers side (35% tint). My rear windows are tinted 5% so not much can be seen from that view. Hope this helps!