Looking for Specific Info

I have a '17 double cab, off road, Non-JBL stereo. A couple years back I upgrades all 6 speakers which was a quantum improvement over the embarassingly crappy speakers factory installed. Now, I am contemplating adding an amp. No Woofer, no more speakers, no need to punch out the windows, just a bit cleaner sounds that I think a moderate power amp will provide with the upgraded speakers. No change out of factory stereo. I don't want to do splicing and soldering so it appears there are amplifier wiring harness kits available to plug and connect without much effort beyond the actual install and routing the wiring. So here's my questions I hope someone can answer.

(1) Do the harness/connector kits work as advertised? Amy customization needed? What maker is best?
(2) Where do folks locate the amp? I am thinking something small, no window busting power needed. Looks like under the front seats is one approach? Which side? No power seats on my Taco. Seats are heated if that makes any difference. I don't really want to give up the space in the back seat compartments..
(3) Is heating especially thinking a smallish amp (60-100 w) an issue?
(4) I saw a couple of mounting ideas. I don't want to raise the seat up for clearance if that's a possibility with a smallish amp. How do folks attach the mounting plate? Looks like maybe using the seat bolts? Could you double side tape it to the carpets? What material for mounting plate? I am a pretty good fabricator for most materials.
(5) If under the seat, does the amp need clearance on its bottom side?

I'm thinking maybe these questions have been answered in a bunch of posts but after looking at a number, there always seemed to be something that I was not interested in...JBL. adding a woofer, etc

So I am thinking a plug in harness connector, no woofer, just amplify the non-factory speakers at a low/moderate boost (60-100w) kind of amp. Any help would be great. Thanks

 

A lot of info https://www.tacomaworld.com/forums/audio-video.12/

 

I will in the future buy the Alpine mini amp that can sit behind the head unit and run power from the battery. I would use the Red Wolf harness and cut that in half to keep from splicing the factory speaker wires.