regarding a 1978 trans am stereo system...

[Thumprkils]

boxes and unboxed speakers in the back window?
sound like a jeff foxworthy joke to me..

[84fiero123]

go to crutchfeild.com they have a table that tells you what you can put where as far as speakers and stereo, and if you buy your equipment from them they have free tech suport.

http://www.crutchfield.com

[hotrod_chevyz]

my friend and i put a system in a 79 camaro once.
I think the dash speaker was a 3x6.Thumpr is right you can get a dash speaker that is both left and right.I put a radar detector right where the dash speaker is on your car so putting a speaker that close isnt too good of an idea anyways for me.
I would get some mini tweets that are small enough to mount to the plastic trim that goes from the dash to the top of the car.The actual screw that holds the trim on is the same screw that holds the speaker on so you dont have to punch your car full of holes.Then find you some 5 or 6 inch mid range speakers with covers for the doors.The sound is worth the modification but if you arent careful cutting and you screw the hole up,you can ruin the structural integrity of the door.You might have 4x8's in the back in the back dash.Wich suck for sound but make perfect sound holes to hear a twelve or two in a box bolted to the reverse side of the back seat.And you can put some midis in the hole too to bring back the fidelity some.sounds pretty good,and the box in back gives you somthing to hide your amps on or in.You can have a box conservativley made so you dont loose all your room in back.
You could always take the amp you suspect is bad to a pawn shop.have them hook it up and test it,if it works it does if it doesnt then there ya go.I hope your not hooking the amps to each other,or hooking up multiple amp outputs to the same speaker...I have a feeling the stereo output to amplifier input is where your problem is.