I'm going through the same thing with my 2012 35is. It has the standard system WITH Nav. I really just wanted the premium enhanced sound from the factory (the only option this car didn't have) but everything else was right and I figured I could upgrade it on my own. Who knew it would be so complicated.
I just wanted the stock upgrade. Maybe I can buy your premium enhanced speakers when you get the JBL's.
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J Ryan
RETIRED: '86 e30 325e, '89 e30 M3, '02 330ci, '05 330ci ZHP, '07 e92 335i, '07 e92 335i, '12 e89 Z4 35is, '5 f82 M4
CURRENT: Porsche 911s