Did TT not already discontinue the E550?
I think you should check out the 550 sized electric helis that Century have been making since 2005. The first was the Swift 16, followed by their Swift 550SE, which is a C/F version with many other features.
I, and a number of others here, have been flying them for many years now. They are easily set-up to be gentle trainers or pretty hot 3D performers using 4S or 5S or 6S packs.
They just introduced the Swift 550NX a couple of months ago.
http://www.centuryheli.com/products/...?currentid=654
There is a lot of info about them, since their introduction, on many forums dedicated to the larger electric helis on the net.