Question E55 AMG vs C6.5 A6 or S6

Hey guys so I have been looking at getting out of my C5 S6 and into something newer and faster. Anyways I have been looking at a few C6 S6 and a few C6.5 A6 3.0T. I really like the cars but the other day I had a friend recommend me to take an E55 AMG out for a spin, I did that… DAMN that thing is quick! I loved the power, the interior was nice, the car looks beautiful and sound amazing, the best part is, is that it’s in my price range! So I’m not very familiar with AMG’s and I thought I would ask you guys if you knew anything about them. Reliability, and known issues. I have looked on line but I still need to get used to other forums. I am mostly on AZ. Do you guys have any pro’s and con’s or S/A6 vs E55? Also does anyone know of any good AMG forums?
Thanks guys! ???