I'm not sure if this is 100% correct but here we go:

I had somebody from the USA asking me if it is possible to install the AMG Advanced Mobile Media System to US E55 AMG with US COMAND.
Unfortunately it seems that the US COMAND won't have a DVD playing option (as the german COMAND has).
So installing the Advanced Mobile Media System is actually impossible.

Only solution for now: US customers with US COMAND have to bring their car personally to AMG in Germany and have the Advanced Mobile Media System installed there.
This includes a DVD changer and two TFT monitors in the rear.
Can't say much about a price tag but it won't be cheap.
I heard something about 3500 EUR as a starting price but I'm not sure. Depending on options and needed modifications, it can cost much more.