I'm using a JL Audio W1 10". It's a shallow mount, about 4.5" deep. It hits hard, it doesn't have as much power as an L7 but it hits hard enough for the cab space. I bought the box separate on eBay for $90, the sub for $125.
I also have a JL but mine is a 10" W0 the w1v2 did have was about 1/2 to deep..but It sounds perfect in this size of truck with 300 watts going to it and 100 going to a component system up front
Mine is an alpine mono 500w. Supplies plenty of power. I have it only ran to the sub. I don't have an aftermarket head unit, i'm using the stock 6disc pioneer.
the jl w1 sounds great in the under seat style boxes and it is a shallow mount, that's what i am running and its only 150rms watts but i feel the amp needs and upgrade.
I thought I would add some information for you on the subwoofer for under the seat. I am using the new Kicker L7 8 inch and it sounds great. It has more than enough to really pound while sounding great as well. I emailed the guy who sells them on eBay from Rodneys customs a few times and he was helpful. I did not end up buying his set up but made my own box which is a little smaller than the .45 of the boxes on eBay. I also got the sub and amp from sonic electronic which seems to always have the best deals. I got the brand new l7 for around $180 and I am running it with the brand new Kicker 400.1 which I got for around $160. It is a really good match for the sub. If you go with the L7 you could probably use the Kicker 500.1 amp that is around $200 most places and will be more than enough power. I hope this helps a little.
