Adding a powered Sub to a JSW?

I'll start by stating, I am far from an electrical guru but I have been successful at installing a new head unit, door speakers and powered sub in my truck a few years ago because of the nice kits crutchfield puts out. But I am curious to know if I can plug in a powered sub into the factory head unit and how might I go about that?

The sub is an 8" Sound Ordinance from Crutchfield that I installed in the above mentioned truck. I don't have the truck anymore, but kept the sub (more or less).
https://www.crutchfield.com/S-fpIjm2v7Tyj/p_777B8PTD/Sound-Ordnance-B-8PTD.html

Also, I haven't looked too closely at installation locations, but I don't want to sacrifice any cargo room if I can avoid it.

But if it's as simple and running some wires under the carpet, plugging and playing, I'd like to add some bass! If it's a little more involved, then I will shelve the project for now.

Your sub also has speaker level inputs so you can just tap into the cars rear speakers for signal. Then you will need to run wires for power and trigger and provide a ground at your mounting location.

When all else fails, read this:
https://pdf.crutchfieldonline.com/ImageBank/v20140414162100/Manuals/777/777B8PTD.PDF

Compliments of Crutchfield's:
https://www.crutchfield.com/Learn/Learn/learningcenter/car/subwoofer_installation_guide.html

Thanks! So assuming the OE head unit doesn't have low level RCA jacks, then I can tap into the factory speaker wiring (via splice) and as long as I keep the polarity correct, I should be good?

Power needs to come from the battery? Now I suppose I should look a little harder for somewhere to stash it.

You could tap from the power port in the trunk if the power port fuse is 15 amp or greater. (The fuse on the amp is 15 Amps) Most people will run power from battery. Even if you don't use the power port for power, it would work fine for the trigger wire because the power ports are usually switched on a newer Dub.
From what I found on the Internet, the power port fuse is 20 Amps. However, both power ports run off of the same fuse so if you were using the sub, you would not want to run anything off of the other power ports that draws much more than a cell phone charger or 2. A 120 volt inverter and the sub run at the same time would blow the power port fuse.
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From the sub owners manual: You don't need a trigger wire. If set to auto turn on it will power up anytime there is signal going to the car speakers.

Great info! Thanks! Usually we only pull power from the ports to charge cell phones. I don't recall even doing anything else with them.
I contacted crutchfield and inquired about the signal connectors for the High Level inputs and they don't sell those separately and they had no info on what they are. But I've seen them on RC batteries and they appear to be a Tamiya connector or similar: