I finally found my dream E39 M5 a few months ago - it's a delight! Well, except for the nav/radio unit and screen. So, I decided to upgrade. I bypassed the many Chinese units on eBay in favor of the Avin Avant-4 unit and have no regrets. Here's a brief report.
I ordered the unit, wireless backup camera, wireless external TPMS, Apple CarPlay, etc. for my car system which already had BMW nav and DSP amp. It came soon, boxed nicely with a lot of stuff. Their website (www.avinusa.com
) shows everything. I used a video showing how to install and wire for my E39. It wasn't perfect, but got the job done. Very helpful was another video in the M3 Forum.
The Avant-4 is impressive. Rather than describe all of it here, just see their website. It fits the E39 dash perfectly, looks like built-in, and works flawlessly. Installation is not easy, but it's very doable to those who like upgrade projects and have some time to get it done.
Unfortunately, the instructions are miserable, and customer support is spotty. Once installed, I had to go to a number of videos and procedures and download and install various apps to get the various options working, but they are working with one important exception - no sound on my car system. That's a biggie, and it's something others have experienced. Hopefully Avin will help me resolve it soon.
Anyway, overall, it's a worthwhile upgrade. My cost with all the bells and whistles was around $850. Certainly not cheap, but it gives a lot.