IMHO, the 9770 has a lot in common with a 2388.  Not because they are similar machines, but because they are a mature, solid, dependable evolution of a base concept.  They also both pretty much evolved to the inherent limits of the frame they were built on.

My advice would be to go spend some time crawling around on the 7120.  Flagship combines are really neat machines, but a totally different animal than your old 2388s.  I think you would like it, as long as you have an open mind and are willing to tackle the learning curve.  Kinda have to forget a lot of the things you knew about combines before.