My e92 came with one of the upgraded factory systems, can't remember which one, and it was still absolutely atrocious. Girlfriends car has factory HK system and it's just about as good as an early 00s Avensis.

I had a full aftermarket system installed as I have to have decent sound quality in a car and tbh it's still not quite where I'd like it 1k later.

To upgrade the entire set up to a really top end system will cost properly big money and you really need to do your homework before hand. If I was to do it again I'd go for a Bavsound setup.