single 18 in a single cab

Think my next build is going to be an 18 in my single cab, running off my AQ 2200 @ 1 ohm. Im wanting to do a big wedge shape box, because I have about 5 ft across to work with and a good amount of depth for a single cab. If needed, I can take out my middle seat and have part of the box go there or something.

What sub would suit me best? Im wanting to tune low for daily driver.

Any help or design would be appreciated.

thanks