I'm in my early 30s with a E55.

My recommendation is to pay more attention to the other differences among the cars you're choosing than the image they give you, really.

The M5 is a good choice if you prefer the control of a stick shift at all times but require 4 doors. The new M3 will most likely handle better than the M5 on the track due to its lighter weight but will probably not be as quiet and relaxing on the highway.

The E55 is the best choice out there if you want to have a high performance automatic sedan. It's much roomier than the M5 especially in the back and with its automatic transmission, it carries a most practical dual personality. You can drive it like a limo or have some serious fun with it.

The performance difference between the M5 and E55 is so insignificant that non-professional drivers can extract more out of a E55 in real world situations.

As far as the image thing goes, the E55 is perfect for speeding given its old man's car conservative image in front of the cops, that's what matters more to me.