I'm planning on buying the dual ported fox acoustic down fire box for my 2012 ford super crew and have narrowed my search down to these 2 subs. As you may have seen in my earlier post, i listen to lots of different music and like a good quality deep bass, as opposed to the "rattle the trunk" sound.

 

jl. cleanest bass. remember to buy a quality amp as well. poor sound can also come from an amp. jl and jl is a sweet combo if sound quality is what youre after

 

There's a lot cheaper amps out there that'll perform as well or better than a jl amp.

 

With 6.25" of mounting depth you have quite a few options.

The new Alpine Type-Rs are engineered to have a nice flat BL curve --> low distortion = SQ
Dayton Titanic MKIII or Dayton HO Reference are both highly regarded subs. The HO will sound slightly better but the Titanic sounds good and will get louder.
Image Dynamics IDQ is another fantastic sounding sub that will work well in that box.
Boston Acoustics G3 - At 6 5/16" mounting depth it will be a close fit. Its on sale at Crutchfield - its a hell of a sub for $100!
CSS SDX10 is a sub that uses an XBL2 motor - it should have fantastic SQ. http://www.creativesound.ca/details.php?model=SDX10

These are all subs I would run in that box and are much better than either of the subs you're looking at.