Generally speaking, electronics should not be too hot to touch. They can get pretty warm sometimes though.

You might check speaker wiring (as much as you are able) to make sure there are no frayed wires that could cause a partial short and overcurrent. But you'd probably have channels dropping out or scratchy noises and such if that were the case.

i moved rear door speaker to front door location. seems to work so-so? i think the volume seems to be favoring the pass side when i listen carefully. i think that is an illusion since the door speaker is mounted down low and your legs block the sound? i opened both doors and got down and listened to both speakers and i think the driver speaker is a bit lower in volume. so maybe the rear/now front speaker is sketchy? how hard is it to replace the factory speaker since it has a plastic "pedestal" base? do you replace the speaker after you pry it off the plastic base?

What does HU mean?

head unit. another odd thing. i am connecting/unconnecting battery to do work on motor and i can hear a pop/crackle sound from door speaker when i reconnect it. this is with doors closed. the pop/crackle sound can be heard as i am connecting battery terminal. and radio is off of course. as the ignition key is in the off position

Sounds like you might have a ground loop or short somewhere. Being you also have issues with your front driver's speaker, I'd start there and trace your wires to that speaker. Could explain all 3 symptoms

Hard to tell about that plastic housing from that angle, but you should be able to replace a speaker in any car with the same std. size, so that plastic housing must come off. I have not seen anything quite like that before.

i replaced speaker and it is better but not great. still no bass but mids seem ok. it is 2 wires to the speaker and it is a single driver and 0-4000hz seems missing but 4k-8k seems to be there. no it is a base system, not bose or anything like that. the door has a tweeter in the sail panel and that works fine. i looked at bundle of wire going thru door jamb and it is taped so i wiggled it and the bass kicked in? the bundle has wires for mirrors, locks, window motor and speakers so it is 12+ wires and they are all cut and spliced? and 2" away is the connector for the union that goes thru the jamb into the car interior and somehow the former owner could not see the connector? i have no idea what type of wiring issues he had. but i think i need to dig up a used door harness at the boneyard

i was thinking of removing door harness but when i pulled the section of wires connected to plugout of door frame i figured i had easy access to solder wires properly. bass is back and i realize that the speakers just might not be that good. i think the crackle from loose wire issue might be gone too. i looked up speaker spacer rings online but there is nothing really like GM uses. the plastic ring cannot be separated from the speaker. a new speaker is $24 or so for a gm speaker. any aftermarket would need some type of spacer or they could be mounted flush in door frame so we will see what transpires.