Most OEM manufacturers still use relatively cheap speakers and still run on the theory that more speakers = better sound (it really doesn’t). What I look for is the ability to tweak the sound – the ZS has a 5 band equaliser and allows you to set the volumes to each corner so you can focus the sound to come from the front, mostly the front or all around. For best sound in the front seats you want the most of the sound from infront of you (all except sub bass is ideal). The ZS requires a certain level of rear sound as the midbases are much stronger behind and add some depth that the fronts simply can’t. So a premium sound system with a decent, programmable equaliser and I can get the best possible sound, usually the premium sound might add some deadening behind the speakers, improving their sound for little extra cost.
Its whether the in car audio tuned by Bose for example or Bose simply supply the equipments. As long as we remember its a car and not going to be a dedicated a Hifi system wewill be on a winner. That said some cars have tremendous systems in them, of which the Mazda CX60 Bose set up was excellent and imo better than the Bose in the i6. Meridan is equally a good premium system. My mate has Meridan in his Range Rover Evoque and it is outstanding. My Tuscon Ultimate has Krell, also premium but, its crap, so I guess it how manufacturers implement them in their cars. I do wonder what it would sound like, if I could retrofit my amp and Kef speakers in my car lol.
Hope your Christmas going well.