P38 Harman Kardon Nightmare

What exactly is wrong with it? Does it sound bad? DA conversion is done at the CD changer, so changing the head unit won't help the sound if you plan on keeping it and using the amps in the doors. Good luck on getting another head unit to work with the steering wheel controls, BTW...

The head unit and door/base amplifiers are designed to work together as a unit, and as such it's not possible to use the amplifiers with any other type of head unit. I've tried! I "lost" my head unit and tried many specialists who said they could make an adaptor, and failed. The best result I got was a continual gentle buzzing through all speakers, the worst was severe hum. The only cure was a replacement genuine head unit. Why do you want to change it? It works and sounds excellent. You won't get a better sounding sound system without removing all the speakers, amps and associated cabling. The steering wheel controls won't work anything else either. If you've not got a CD changer in the boot, that's relatively easy to add though.

Alan C '98 4.6 HSE P38A '89 3.5 EFi RRC

I'm guessing you have the later simpler HK system without the door amplifiers then. It's easy to drive the rear base amp/speaker and all the other door speakers on this system as virtually any head should work fine. Also, the original head unit wasn't the same quality as the previous system, so changing it will improve the sound quality, especially if you require MP3 playback etc. Though there's still no way to couple the steering wheel controls to anything else mind.

Alan C '98 4.6 HSE P38A '89 3.5 EFi RRC