It's not nearly as bad as I thought it would be. The unit is a JL Audio ACP108LG-W3v3. It can turn on when a speaker signal is detected so no need for a remote turn on wire.
I ran the 8 gauge to the left of the engine to the side of the vehicle close to where the rear wiper fluid tube goes. Take the center trim (between B-pillar floor trim, and footwell corner trim) off. Then take the footwell trim off (has 1 fastener). There's an unused grommet next to the rear wiper fluid tube grommet. You'll want to take that out. Next, take out the signal indicator on the body. This will give you space and vision to fish the 8g wire and push it through the grommet hole (i used a metal hangar). Drilled a hole into the grommet and pushed the 8g through it. Reinstalled grommet with the help of soapy water and screw driver.
At this point ask yourself do you want to just run the wire to the back or remove panels so cables (8guage power and speaker wire) are not seen. If you don't care about the wire being visible, then most of the work is done. Just need to tap (i soldered) the speaker wire in the wire loom that leads into the b-pillar. (red + rear right, brown - rear right, these cables change colors at the door loom which then lead to the speaker itself) and re-install trims. Tap back seat bolt for ground. Connect wires to amp, and job is done !
I went the no wires visible route. For this you'll have to remove everything from the trunk except the spare tire. Center trunk trim pulls out. Right side trunk trim has 3-4 fasteners that need to be removed (i used a flat head screw driver) then it pulls out. Right side rear lower trim (goes under the seat a little) pulls out. I only unfastened the lower part of the b-pillar trim (you'll have enough room to fish wires with a metal hangar). Run wires and re-install trim carefully.
I have the stock headunit (without RF) that has the apple play feature. This powered sub adds a sweet low end to a system that was almost completely missing it. This powered sub is kinda expensive if you want to just get some low end, but I had it laying around from a previous car. If all you want to do is add that missing low end, you could spend a lot less. The wiring kit I used was $29 from sonic electronic (no rca wire), and you could get a Sound Ordnance B-8PTD (cheapest I could find) which also can turn on with a signal from the speaker wire for $170. Around $200 to get some low end. What do you guys think ?
*thank you to inuvik for posting the wiring diagram (https://mirageforum.com/forum/showth...ll=1#post74122 post#2)