Just bit the bullet and installed a powered, enclosed subwoofer. After doing a bunch of research I decided on the Cerwin Vega VPAS10. It's a 10" Subwoofer rated at 450 Max/ 200 RMS. The main reason I decided on the Vega instead of say the Kenwood or Kicker (both have great ratings) is that its a solid 10" sub. The Kicker is an 8" and I didnt like how they came up with a wired plug for installation. The Kenwood is an oval thats like 8x5 and not very powerful. Also, the Vega, even though it is a larger speaker, had the shallowest mounting depth. I believe its something like 2.6". Installation was straight forward. Mounted it with velcro under the driver's seat of my 1993 Toyota Pickup SR5 ext. cab. I did have to lift the rear of the seat by about an inch just to give the speaker some "breathing" room. I accomplished this by grabbing two 1" lug nuts that I had lying around, putting them between the seat mount and cab floor as spacers and bought some Grade 8.8 M10x1.25 (40) bolts. I kept the gains on the actual sub enclosure dialed all the way down and controlled the sound with the EQ on my JVC kdr775s head unit. Does a great job filling the cab with deep bass (35 hz low pass filter). Wont set your neighbors alarm off but will kill some brain cells if played too loud. It is nice having a 10" sub in my truck and it literally taking up 0 useful space. Just thought I'd share my experience since I had a very difficult time actually finding human reviews on these types of speakers/enclosures. If any one has any questions please don't hesitate to ask.
my only concern would be that your speaker wire (maybe a ground) looks kind of vulnerable hanging out there like that.
maybe it is a non issue if you don't slide the seat back and forth a bunch with kids/dog hopping in the back
No kids. I try to never move the driver seat, I have it set just right! I needed the long ground wire to be able to move the sub without having to mess with the tiny aluminum set screws. Which is probably my only complaint about this speaker. Those tiny fragile set screws for the Ground/Power and Remote. The Pioneer looked good too but was very similar to the Kenwood. Weird oblong speaker.