MrMoose

After going through a couple iterations I've got the stereo sounding pretty good on my 987.2 Cayman, figured I'd write up what worked for me as maybe it'll help someone else. I like listening to tunes while I drive but I'm definitely not a big audio system guy: mostly just trying to get something that worked better than the stock speakers, which even I could tell were kinda meh. This is with a non-Bose system.

Door Woofers: Alpine S2-80C 8" ($160). The stock woofers are pretty shallow and most 8" speakers are too deep to fit, but there's an easy fix. Remove the stock speakers from the doors and then remove the speaker from its plastic frame. Using side cutters clip out the center grille portion of the frame, and then mount the Alpines on the front (just drill pilot holes in the plastic and then use the Apline's screws to mount them). The frame screws into the door and the speaker screws into the frame. I soldered wires with terminals onto the inside of the existing connector in the frame to connect to the speakers, this let me use the stock wiring harness connector.

Door Midrange: Audiofrog GS40 4" ($270). These mounted right to the door panel, I may have had to trim the plastic or the speaker ears slightly. The OEM midrange speakers had capacitors mounted to them, IIRC it was a ~400Hz high-pass. Since I was using the stock ASK amp I assumed I wanted to keep the crossovers similar so I added 300Hz inline bass blockers from Crutchfield ($10). For these I just cut off the stock wiring connectors and crimped on new terminals.

(Note that these are very nice speakers, but if I were doing it again I'd probably just get the Alpine S2-40C 4" ($104) to save some money. Since I'm not relying on them to produce much low end then I suspect those would likely be more than sufficient.)

Dash Tweeters: I used the 1" tweeters that came in the S2-80C kit with their included 7kHz inline high-pass filters. The stock tweeters have the same cutoff capacitors so I figure that would work fine with the ASK amp. The Alpines would probably fit okay in the stock tweeter location, but I'd hacked up the plastic mounts to fit some other tweeters earlier so I just double-sided taped them in place. Again, I cut off the stock wiring connectors and crimped on new terminals.

Center Dash Full Range: This is an odd size and I wasn't able to find anything that matched exactly. The OEM speaker just seemed to produce too much sound, though, and mine was pretty sun-damaged at this point so I wanted to replace it. The Sundown Audio SA-2.75 FR V2 ($60/pr) is a full range speaker that fit with some modification: they're okay in X and Y but they're way too deep. I ended up using a Dremel with a 90-degree adapter and a cutting bit to *very carefully* cut away the plastic under where the speaker mounts to make room. Then I ground the mounting holes on the speaker inwards about 3mm and was able to mount it using the existing holes and screws. Again, I cut off the stock wiring terminal and crimped on new ones. No crossover added here: the stock speaker didn't have one, nor did the Sundowns: either the ASK has an internal crossover or these are just getting a full range signal.

Rear Deck: I had replaced these a long time ago with some cheap Rockford Fosgate R14X2 Prime 4" two-ways ($60) because one of the OEM speakers had a dodgy terminal. But unless you're having similar problems I would just leave them stock because you're not relying on them for much. The issue is that they're a real pain to get to and you're very likely to scratch up the interior doing so

Again, definitely not a big audio guy, but it sounds significantly better than stock and I'm happy. It's plenty loud for me, the bass is strong and not muddy, vocals are clear, and the sound seems well balanced. After playing around a bunch I've got the loudness feature on (it does a decent job of keeping the bass linear with volume) with bass -3 and treble +2.

FlipE

I'm not super-picky. Cayman sounds fine to me. I thought the Ellse was OK, even though the audiophiles say it is awful. Well, I didn't use the audio much on the Elise. The factory Bose stuff in my Suburban sounds OK to me, and the 6-CD changer is nice on a long tow.

The sound in the cab of my Chevy Kodiak on the other hand clearly stinks. I can put in a CD when the motorhome is parked and listen the crappy sound, then walk to the back and the sound from the speakers in the bedroom is damned good. Some day I'll upgrade the speakers in the cab, as decent sound on long tows would be a good thing.

nicetheory

Mr.Moose, was your 987.2 equipped with the non-bose CD30 Sound Plus option? Mine was not, so I my car does have rear deck speakers at all. Am curious if the wiring looms are just there or not.... I've not spent any time on this, but I am assuming nothing is back there until the grills. Edit: it also doesn't have a center dash speaker, just the center grill.