need opinions on speaker upgrades for 87 300e

[dirtysocks]

O. K. Here is my situation. I bought this car with a panasonic 40 watt x 4 head unit, still running through the front and rear speaker fader on the center console. The car had some other work done as well. 2 pioneer 6x9's are mounted where the backseat headrests fold down into, and they run off an alpine 80 watt amp. The two front dash speakers were replaced by 4" infiniti 421i's, or something like that.
These two infiniti's were installed very poorly (one screw holding the left speaker in and two holding the right, screwed directly into the soft, thin dash material.) The infiniti mounted to the right buzzes cosiderably and I believe it is the speaker and not the way it is mounted because I removed it, with no sound improvement. This I don't quite understand because I was under the impression that the fader switch in the center console would cut the wattage down to 20, hardly enough to make a quality infiniti buzz.
Anyway, I just removed the stock rear shelf speakers, the only stocks left. I just threw some pioneer 4" I picked up on clearance in there for the time being, but they are not mounted, as they are only temporary.
Now, I have no baskets or anything now for the front dash speakers after the crappy install, so I would imagine there is no way I could put rainbows in easily (which I would like to do). I am not opposed to putting the pioneers I already have in the back shelf in the dash, they fit well, but I would need to make a template. This I am not sure how to do, but I know some on the forum have, so any input on how to would be appreciated. I am also assuming I would have to make a similar template to put 5.5"s in the rear shelf, is this true or is there a way around it? (I have those baskets)
One other option I was considering was putting a 12" or 15" in the trunk and leaving the rear shelf holes open, thus letting the bass travel through the holes. Any opinions on this?
Well, I thank you for reading this long involved post about my speaker troubles. As you can see I have many options and decisions to make, and any and all input that may help is greatly appreciated. Thank you again for your time.

[dirtysocks]

Okay. Maybe the last post was too long for anyone to get through. Well, I have managed to attach a pair of 4"pioneers to the rear speaker baskets, and I was just wondering if shoving door weatherstripping into the cracks between the basket and the speaker would be an adequate sound insulator? I am against glueing or caulking anything unless that is the only possible solution. The stripping is a semi-thick foam rubber, actually quite similar to the stuff that rises up around the rear speakers. Thank you for your time.