The '06 4.4 is nice - you'll like it. But get the sport package - the better seats alone make such a big difference I can't imagine not having it. $16k is about the ask for similar examples in my part of the country, so that doesn't seem crazy out of line. Of course, you'll be able to do some better after negotiations. Good luck.

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2013 X5M - Sapphire Black
2006 X5 4.4i - Sapphire Black
2002 M3 Euro - Alpine White
2003 M5 - TiAg
2003 M3 - TiAg
2010 535i - Deep Blue Metallic
2007 530i - Deep Green Metallic