First post here, I'll get the quick intro out of the way.
I work professionally in the automotive industry, starter as a mechanic a long time ago and own my own business in the after market world of car electronics.
Started 18 years ago in a car audio shop and haven't looked back since, I am a busy professional with years of experience in this environment.
I also own 4 BMW ranging from a e31 V12 a couple e36's (1 M3) and this recent
Purchase E53 (2006 sport package, 4 corner air 4.4 imola red 42,000 miles)

Ok, enough about me.

This E53 has factory Nav and DSP, it is a fully optioned car for audio/phone.

I bought this car for my wife and flew down to cali to pick it up, even brought a factory AUX cable so the drive home to Oregon wouldn't suck.

As it's my wife's car I thought I would keep things simple and just replace the failing screen.
I did that but the aux cable and USB cig charger and all its cables is annoying.
I am a pioneer and Sony dealer along with being able to get Kenwood and alpine, I've built plenty of X5's in my day and wasn't looking to go that route, don't have time and my wife doesn't need anything more then how the factory system sounds.
so after replacing the factory screen I was constantly annoyed with connectivity and how bad the factory screen washes in the sun.
Started looking at the direct fits and bought the GA7166A.

It had a lot of cool features and the direct fit and factory interface had me thinking it was a good deal.
Well, to clear up if it works with DSP, IT DOES. All controls worked and functioned, what didn't is the sound.
It doesn't match the factory volume output and the deck at high gain has lots of distortion. I'd say it comes in around 65% volume.
Shame, I really wanted to like this unit.
Sadly it didn't get pass being plugged in in the back for testing.
Too bad.
This issue might be caused by the auto leveling the DSP does at start up, I don't know if this is a 2006 up problem but either way even if I coded that out the amount of distortion this unit produces on its own is garbage and I'll I would end up with is louder distortion.

Anyone used anything different keeping the factory DSP they like?