Do you have salvage yards there (where they take the crashed cars)? Get a used one out of a salvage X5 instead of a new one.

Did the dealer tell you why it is blown (wiring issue or just bad luck)?

Best scenario is to go with an aftermarket amp and speakers, but I don't know what they sell for in your country. Here in the USA they are pretty reasonable for great sound. You'll need a line out converter to convert the signals from the head unit to the amp into coaxial (RCA) cables, but you can use the existing BMW speaker wiring so it is not a complex install.

Good luck!

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual