Haven’t heard the Forte but I have compared the Heresy and Cornwall. The biggest difference is that the Heresy is coming from the floor and its noticeable. I love the look of the Heresy but that’s the main issue that’s keeping me from buying them. I think they lose the coolness factor when on stands. I'm still going back and forth between the Heresy and Forte and remain undecided. The Forte is a significant jump in price, and I'm not a fan of their generic look, despite them likely solving the Heresy's main shortcomings (height/bass extension).
The Heritage line shares many of the same driver components until you get to the La Scala and above, but the horn shapes, and sizes of the cabinet will have a large impact on the overall sound, mostly in terms of scale and sensitivity.