not sure how to vote. I have kept my M3, I am the original owner of a 2008 E90, but have since added a Cayman S, NSX, and Jeep Cherokee as a winter beater.
I would only sell the M3 for an Aston Martin V8 Vantage (6 speed only) R8, or another Porsche 911 4S/Turbo.
2008 M3 sedan, Interlagos Blue, Tan Nappa leather, 6 speed
2008 Porsche Cayman S - 6 speed
1995 Acura NSX - 5 speed
2005 Cherokee Limited (winter beater)