Looks nice!
The small (22ga?24ga?) black wires did go to a loop antenna on ours, like what Ron linked to.
The subwoofer under the bed is 'useless' for good sound IMO. I have yet to get around to going in there and taking it out, it has remained in there due to being out of the way.

The small surround speakers are a close second in audio quality. Better than nothing, but not better than what came on the 32" TV I put in. We just use the TV sound.
I bring any media we want to watch on a USB stick, and plug it into the TV. Fulll HD 1080 is not problem. I skipped Blu Ray disks, and bring the HD content this way. The double layer Blu Ray holds 50GB of data, and is a delicate media. Scratch the label side of it too deep, and its trash. The optical side can be polished QUITE a bit to restore disc use.
I use a 256GB stick, it can hold 5X + the media of one disc, and can go through the wash without damage. I didnt WANT to prove that, but have by not checking pockets.....

I see that the head unit you linked to also takes USB, might be something to explore.
(edit to correct spelling)