Nashy

Hi, I’ve just bought a 2013 3.0 Q5 line plus which has quite a few upgrades including the B&O sound system. As per a million other online posts, the sound quality is not what i expected and I’m looking to upgrade it if possible. I don’t want to go mad, or have a huge sub in the boot, just improve the quality a bit especially the bass. Lots of varying opinion, ideally I’d like the minimum fuss. Has anyone changed their sub with good results or is there any advice on this please ? Thanks in advance.