I have a 2006 Screw with non-audiophile sound system. I replaced the stock speakers with some nice Alpine's that do the job except for the low end (to be expected). I am not looking for anything to win shows with, just compliment the other speakers.
I got a Crutchfield catalog and these caught my eye:

Kenwood KSC-SW1:

dimensions: 15-3/4"W x 3-11/16"H x 9-1/16"D

Kenwood KSC-SW10 (this may be the newer model of the above):

dimensions: 14-1/2"W x 3-5/8"H x 8-7/8"D

Blaupunkt THb 200A:

dimensions: 14"W x 3-3/8"H x 8-15/16"D

They seem like they would be great since they are powered and are very compact so that they would fit under the passenger seat (maybe) and would be out of the way. Like I said, I would never expect to blow anyone away, but just looking to add some low-end.

 

Holy crap, those are tiny. I dunno, I've never had any experience with the Bazooka bass tubes, but from what I hear, they pack a decent punch for the size. Maybe get 2 of them? They won't blow your neighbors away, but if you are just looking for something for yourself (and not to show off with), the Bazooka tubes should be sufficient.

 

I would add a single 10 inch sub under the back seat or even an 8 inch, nothing fancy but something with good SQ to work with your mids and highs. You can pick up a single 10 box thats made for under your seat for cheap at most websites or even ebay. Also, Depeding on your sub choice, i doubt one 10 that will fit would need much power so a smaller amp would fit very nicely underneath the passenger seat.

 

The issue I have with putting a larger box in the back under one of the seats is loosing the space. We regularly flip the seats up and use the space under them for shopping and such, so I was trying to get around that.

As for the Bazooka tubes, I had a buddy that had one back in 1991 and it did o.k., but where do you put them? More than likely, they would have to go under the back seats (if they even fit) which once again, I would like to keep open.

 

I cannot speak specifically to the boxes you listed above, BUT.. About 3 years ago I bought a Kenwood self powered 10" for the back of my wife's (at the time) Taurus. I paid $299 on sale at Best Buy for it. It was underpowered, didn't carry far, and overall was unimpressive. Perhaps they've come a long way and are great now, but I was forever turned off to all-in-one retail solutions.

 

Like I said, I don't have them, but I think they are RELATIVELY compact. I mean, if you can fit the pre-made sub box (like you gave pics of) in your truck, I doubt the Bazooka tubes would take up any additionaly space. Check the specs on them -- they may even fit under your driver/passenger seat...