On my 2007 997.1 Carrera Cabriolet, the solution was to replace the PCM with a Pioneer NEX system, which incorporated an excellent microphone system and GPS. The PCM is a “Double DIN” size component which allows for many aftermarket systems and up to date features such as Apple Play or Android equivalent. It helped that my car had the BOSE option, so speakers did not need upgrading.
Of course, the original radio is now safely boxed in the garage, to be passed on to the next owner if I ever sell this car, which seems unlikely.
I did a similar upgrade to my 08 C2S Cab last year, but I chose a different head unit (Alpine ILX-107). I picked that head unit for two reasons: 1) I’m a huge fan of Alpine Sound quality and (2) wireless Carplay. I’m an Apple guy, and this is my car so Carplay was important.
I did it myself over the course of a Sunday afternoon. It wasn’t massively challenging, so long as you followed closely the instructions you will find on Rennlist forums. Mine was also Bose, and so I hummed and hawed most of the winter, trying to decide if I would bridge the fibre optic network between the head unit and the amplifier, or it I would just replace the amplifier as well (it takes in a digital signal via fibre optic).
In the end, I bought a $100 adapter off of Ebay to bridge the connections, and it worked just fine. For reference, your stock head unit uses a Fibre Optic network to send pure digital signal to the digital Bose Amp. The Alpine/Pioneer/Aftermarket head unit does not have this connection – it only has RCA connections out of it. So you have to bridge it with something.
It was tricky, but not impossible, and I got it all right on the first try.
The other thing I needed was that the Alpine installation requires a connection into your brake lights wire because Alpine only lets you access the advanced settings of teh unit if your handbrake is on (ie you are stopped). A $15 defeater (again on Ebay) fixed that problem, and I just wired it into the install.
Bottom line was that the sound quality went from marginal to beautiful, using the same amplifier and speakers as stock. That is to say, the amp and speakers aren’t the problem; it’s the stock head unit that sounds like crap.
Yes, I did lose the navigation details in the tachometer display, but I don’t care. Carplay more than makes up for that.