Yep, the E55 sure is an old mans car. At my ripe old age of 42, those 40 YO women at the geriatrics center are amazed at how spry the car and I are! The E55 is a performance oriented sport/family car.
First, you really need to think about the type of car you really want. You can compare the E55 and the M5, but the M3 is in a different class-and that's not just cost. A test drive of all serious contenders in in order.
Decide how much you want to spend. In the 80K range, you have the E55, M5, XJR, A8. All have their good and bad points. I bought the E55 because of the rear seat room for the kids and the automatic tranny. My wife refuses to drive a manual with 3 kids in the back seat in NY traffic.
This old man, his E55, family and friends can be in the car and all witness the old mans car blow away almost any sports car out there (except 4 Michael's 500E, which I think is a bit stronger than other examples )
The M3 costs less, and while it handles and brakes really well, will be left in the dust by any of the cars listed above on the straights. If I didn't have a wife, 3 kids, 3 BIG dogs and a cat, I probably would not have bought the E55. Porsche, Corvette, Z8 all come to mind before the E55. I had a Cadicrap STS which was a fairly quick family hauler, but quality was non-existant and it was in the shop all the time. WE LOVE THE E55-it's FAST, comfortable for a family of 5, safe, handles and brakes like a sports car and it's stealthy.
I have some magazine articles posted to the E55 Registry home page-check em out if you want...Choose wisely.
Gary

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http://clubs.snap.com/mercedesbenze55registry/index.lhtml
00 AMG E55
96 DCM Impala SS
94 ZR-1
81 Corvette Cpe