I went with a Rockford Fosgate P3 Punch shallow mount 10" subwoofer, mostly becuase I couldn't get my hands on the sub I wanted and it was the next best fit for a very small enclosure. AIK, RF asks for 0.4-1.0 ft^3, with ~0.6 ft^3 being optimal for a sealed enclosure. I built my box to roughly 0.36 ft^3 and stuffed it with a 1/2 lb of poly hoping to 'increase' the volume a bit. Honestly, it sounds slightly better with the poly in it, but the box is just too small. When the weather warms up I'll build another one. The reason I didn't go bigger was to save 100% of the room under the 60% bench seat. As is, I can lift the 60% split up and the box doesn't intrude, at all.
That said, the sound isn't great. It doesn't hit very hard and distorts badly at moderate volume. This is partly due to the fact that I don't have an EQ, nor does the factory stereo. The only control I have over the sub is the gain, and it's low and high pass filters via my amp and LOC. I would probably air on the side of caution and NOT buy this sub, since it doesn't seem top respond well below ~45Hz and becomes very muddy above ~80Hz, making it better suited as a mid range driver rather than a sub, IMO. This could be an enclosure problem, so I'll post an update when I replace it.
In RF's defense, I've heard some good reviews on this sub, and I havn't written it off yet.
Power is from an old Pioneer GM-5000T, which is well suited to the power rating of the woofer. I'm using stock headunit with what I'll call a 'T-Harness' that I used to tie my two amps and line-out converter into the factory harness.. All factory wiring is intact and uncut, including speaker terminal ends.
What would I try if I could? The Pioneer TS-SW250 series is what I wanted, but couldn't find. Secondly, the Kicker 10CVT series. Both have a rated frequency response of around 20Hz, versus the 45Hz of the Rockford.