I like the S6, but the cost of ordering a new S6 compared to my 550xi with Dinan 2 was close to a $20k delta given the $11,300 I received off MSRP of the BMW. Although the S6 is the better performer between the two, I didn't feel the difference was significant enough to justify the 20 grand. Not to mention the fact that it seems as if Audi changes its model's body style every lunar cycle.
Current: 2012 M-Sport 550i X-drive Dinan Stage 2, 1973 911 with 930 Motor (340 hp 2200 lbs).
Gone but not forgotten: 2007 911 Turbo, 2005 911 Carrera S, 07 BMW M Coupe, 07 335 XI, 05 Mercedes R500