I've been slowly getting my original Bose system back to it's original sound quality. I originally replaced all 4 speakers with PowerBass 2 ohm units, which was an slight improvement. Next I had all 4 individual amplifiers reconditioned by
Infiniti Bose Amplifiers, Speakers and Car Stereos Repaired which also helped the overall sound quality. Finally, I recently had the original head unit reconditioned by
Bishop's Vintage Car Audio Repair LLC which included replacing all the capacitors, tape player motor and belts, and installing Bluetooth, and I now have a complete original system that sounds like it did when it was new. Yes, I spent far more than probably makes sense for the vehicle, but I was trying to keep it as original as possible - in retrospect I probably would have achieved equal or better sound quality by installing an aftermarket amp and speakers combined with the reconditioned head unit and would have spent less overall. My goal though, was to retain the original Bose amps which are tuned and equalized specifically for the car - I knew from experience how good the stereo system sounded when they were new and wanted to have that same quality sound in my Q45 again.