Generally speaking the head unit and app are a great idea. The app has a decent selection of options for controlling your sound and works ok. The main issue is the “sub” or “2nd zone” output is not independently selectable. If you’re going to blend those to features into a single pair of RCA outputs then “sub” or “zone 2” needs to be selectable. The issue is when using them as subwoofer outputs the volume doesn’t go up/down with the main volume. If you turn your music right down the subs keep playing at full volume. You have to go into the app to turn your subs down. As a 2nd zone that would be great but not for a subwoofer output. If you could just choose “sub”or “zone 2” in the app and have it so the main volume controls the subs when “sub” is selected then the app would be almost perfect. The other smaller issue is the zone 1 volume screen will randomly change to the main zone 1 menu instead of staying on the volume screen. It does this randomly but happens most often when changing between apps or when you first select zone 1 volume and adjust it, shortly after it’ll just leave the volume screen. Fix these issues and you’d have a killer setup worth 4 or 5 stars. I’ve been installing and selling car audio for 25 years so tech support can contact me if they want more clarification.