Love my Heresy IIIs and did not like the plastic diaphragm in redesigned mid horn of the IVs, preferring the sound of the titanium IIIs. Have wondered if the Forte IV suffered the same as the Heresy. The Heresy requires a good front end for sure, and with that they're great (I use a couple of REL subs with mine).
Klipsch Heresy vs Forte
For those who may be debating between the two, I just posted this last night. I actually like the voices in the Heresy. Deeper presentation but they each have their attributes. Happy listeningÂ