From Motortrend's Head 2 Head, here are two of my favorite cars competing for the hearts of Jonny Lieberman and Michael Shaffer. I still can't decide which is my ultimate, as I've been torn lately between the top two German brands, but they are both beautiful machines. Some stats for you:
BMW M5 Competition Package [3.7 seconds in 0-60 with 1/4 mile clocking in at 11.9 @ 122.2]
Mercedes-Benz E63 AMG S [3.4 seconds in 0-60 with 1/4 mile clocking in at 11.6 @ 121.8]

http://youtu.be/rY5oSik1eHs

Not spoil anything for you but my favorite part is at 13:55 when Shaffer goes, ""We are in the AM-jesus christ!"