You should try to get an X5 amp as you'll have to have the others recoded. They are tuned to the interior size and the X5 is a lot different from an E39 interior, unless it's an E39 touring.

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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