Fi Q w/ Memphis 1000D

I'm new here and looking for some help/suggestions.

I currently have a Memphis 1000D left over from a previous setup (4 - memphis PR 12"s) in a blazer.

I have since sold that vehicle, but still have the amp and speakers laying around. After learning about Fi Audio and reading more and more about them over the past week. I am interested in purchasing one 12" Q to go under the rear seat of my 05 Ext Cab GMC Sierra.

I want to use the existing amp to power the sub. If my memory serves me correct, it is capable of 1100x1 RMS Power @ 1 Ohm Mono (14.4V). I'm wondering if I should add the BP option to the sub to allow for future changes to my setup (ie. addition of another 12" Q and 2400D, etc.)?

I'm also looking for any suggestions on a box design/size as well. I know subthump sells a single sealed down firing 12" ultra deep box for my truck that wouldn't require raising the seat. According to the specs on their site it should be fine other than it doesn't have the optimal amount of air space for a sealed enclosure (only .92 as opposed to the 1.2-1.3 suggested in the recommendations thread). I am also considering having one custom built for my application. Just looking for some suggestions/layouts/ideas.

Would a sealed box be the way to go?

Downfiring/Upfiring?

I guess I'm looking more for SQ.

Any advice is appreciated.

Thanks in advance.