I sold my M3 and removed my stereo before the sale. I invested quite a bit in audio and here are my Hybrid Audio drivers for sale. Hybrid Audio is number one in sound quality right now. That is not just my opinion. It's a fact that they are winning more IASCA sound quality competitions than any other speaker brand.
1 Set of Hybrid Audio Legatia L1 Pro R2 Tweeters
1 Set of Hybrid Audio Legatia L4SE Speakers
I bought them new from a local dealer and had them custom installed. The L1ProR2 tweeters are installed in the stock tweeter pods for the E92 M3. The tweeters are larger than the factory tweeters so that factory tweeter pods have been modified (fiberglass) and painted satin black. The tweeters are aimed off-axis so the sound is soft and beautiful.
The L4SE speakers come with carbon fiber covered trim bezels. The bezels provide a firm surface for the speaker mount (no flexing) and ensures a tight seal against the door panel.
I had these speakers configured in an active configuration powered by Zapco DC reference amplifiers. Loud and clear is an understatement. If you plan on running these in a passive configuration, you'll need a passive crossover. Hybrid Audio provides lots of information on what components you'll need.
Legatia L1 Pro R2 Manual
Legatia L4SE Manual
I paid $1500. for the set installed. I'm entertaining reasonable offers.
Legatia L1 Pro R2 Tweeters
Legatia L4SE Speaker Set