 I picked up an '07 650i coupe for $51K, plus trade in of a '99 M3 with 80K miles on it.  The 650 is a delight (sure, you say, what wouldn't be compared to the rusty horse I'd been riding), and in unexpected ways.  The seats envelope in a way superior to those in the 2009 MB CL I  rented and are far superior to those in the Carerra.  The engine sound is of elegant fortitude, the handling pugnacious when demanded but otherwise smooth and flat-out fun.  The sports mode is a bit jerky at times, but darn quick off the line (the normal mode, which my wife dubs 'the macher mode,' is far less responsive to the pedal stomp yet very smooth).  I feel very safe in it, although the A-pillar obscures a bit.