new build, need advice on sub stage

Hey guys, im doing a build in my buddy's 1999 extended cab ranger. He wants something that will be loud in a small(er) box and on not so much power. 1000 or less rms. He wants it to be in a small(er) box because he sometimes has to use one of the jump seats in da back.

what sub would you recommend? we are getting a custom enclosure made to whatever sub we decide on, he loves alpine and jl products and was thinking a w6/7 or type x. He wants it to be a 12" or nice a$$ 8-10".

also an amp for powering it, dont want to spend much on the amp.

any input will be great! he wants cheap but wont sacrifice quality, so best bang for the buck.
he has a high output alt already putting out 270amps, and rockford 4 guage ofc wiring and big 3, and a nice agm bat under the hood.

thanks for the help guys, and just ask for more info if needed for advice.

Anyone?!

I dont have any other recommendations, but I do happen to have a 10" type X in my ranger paired to a pdx 1000.1 and it's plenty of sub for the small ranger cab. I managed to fit the box behind the drivers side with the jump seat removed and the amp at the back wall of the cab behind the sub box; which left the jump-seat on the passengers side functional.

Being that I am running my type X in a slot ported box it takes up quite a lot of space at ~1.4m3 (as far as cab space in the ranger goes anyway). The box is sitting upright to save space right now. But if you are building a custom box, then you should be able to make use of the space back there more effectively.

Also as it is, the bass easily drowns out the mids of my speakers (infinity reference all around) going to upgrade to amplified components when I find time.