Op: These guys deliver speakers with 3 hole mounting for BMW in good quality:
http://www.bavariansoundwerks.com.
They dont have F20 in their system, but the speakers are probably the same size as in other BMW`s.
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2013 F21 116d Msport
2007 E91 325d M sport
x 2008 520dAT, x 2006 320d M sport, x 2004 320 dA M sport, x 2002 Mini Cooper S