What I have heard is that the individual system is a different system all together and is very hard to get in the US.
The enhanced premium system is the highest for the M but I don't think it is the same as the Individual Sound System.

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2011 ///X5 M (On Order)

2009 X5 4.8 M Sport Space Gray/Black Fully Loaded

2007 GMC Yukon XL Denali Loaded and Customised