There is hardly any difference in the sound system in Audis Sonos compared to Harman Kardon in the i4. The main thing is the bit rate of the music and how your playing it. Don’t play it through Bluetooth, I copied my songs in Flac format to the BMW hard drive and the sound is way better. You can also adjust the settings such as the equaliser. The interior of the i4 is much better looking than the q4 and nothing compares to BMW’s idrive system. I hated having to lean forward to try and do things on the touch screen in the Audi and keep reaching to change the drive select button then accidentally pressing the horrible touch sensitive buttons on the steering wheel. Also the i4 was way more fun to drive compared with the q4 40 that hardly moved when you put your foot down.