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Hi in next few months I am very likely to purchase myself an A4 1.9Tdi sport estate b6 with the the Bose sound system speaker amp etc. I used to own one of these 5 years ago and the sound system is fantastic. Basically what I would like to know is how easy is it to install a more modern stereo unit with Bluetooth, usb etc to enable the system to sound just as good. Is it just a case of plug and play or is it more complicated than that? Thanks in advance