I currently have a Peugeot hybrid. As it’s the GT Premium model it has a Focal sound system as standard which is well regarded on the continent but little known in the UK I expect.
Prior to that I had a BMW which I added a Harman Kardon system at a cost of £600 approx.
The HK was an excellent all round sound system delivering some real booming rock as well as other quieter genres capably, which gave me four years of driving pleasure. The Focal (after three months listening) is slightly more hifi and has a crystal clear tone with more high end clarity, but it can also dish out a loaded bass and loads of undistorted volume when called upon. Both are very good sound systems, but the HK was probably more enjoyable to interact with purely down to the idrive controllability.
( The BMW is hugely superior with its ‘iDrive controller’ media delivery than the rather pedestrian and frustrating ‘touch screen’ control found in the Peugeot.)