Just wondering how good the standard sound system is in the new A3, and whether it's worth getting the Audi sound system upgrade? Obviously having a separate sub will give better bass, but has anyone had a chance to do a back to back comparison to see how much of an improvement there is in the other speakers and the overall sound?The B&O is too expensive for me, but I could stretch to Audi sound system if it's a big improvement over the standard fit.Thanks in advance for any thoughts/experiences!