Hi ricardojoa,
The sonic improvements between the extreme version mono's, and the glass ceiling version mono's to my ears are definitely distinguishable. The Mono Extremes were the best I had ever heard in my system. The GC's are better. I would say around 15% or so. Over all sound in my opinion? Well balanced, good control over the drivers, even those pesky big ones, and very good detail, bordering on great. The Odyssey's tend to be a little on the warm side, but not overly so imo. Some say leave them on all the time, especially Klaus, to get "the best sound". I tend to disagree. If off for several days, like anything, they will sound a bit better after warmed up. With daily use, I turned them off at the end of the day. Like anything, they have their trade offs, just depends if you are willing to live with those trade offs. For the new price, they punch out of their weight class. And, Klaus is nuts, in a good way. You will love working with the guy, his energy can be infectious.
Hope this helps,
JCarney