I'm not aware of any "upgrade kits" available direct from Klipsch, but there are a number of places where you can purchase upgrade and/or replacement parts for Heresy (and other Klipsch speakers). Bob Crites sells crossover kits, fully assembled crossovers, drivers, etc. ALK Engineering sells crossover upgrades as does Dean G. I'm sure there are a couple of others I'm forgetting.
I have replaced the crossovers and all the drivers (woofer, mids, and tweeters) in my Heresy I speakers and have also replaced the crossovers, mids and tweets in my KLF-30s with Crites parts. Not very expensive, not hard to do, and it improved the sound of both sets of speakers.
I have replaced the crossovers and all the drivers (woofer, mids, and tweeters) in my Heresy I speakers and have also replaced the crossovers, mids and tweets in my KLF-30s with Crites parts. Not very expensive, not hard to do, and it improved the sound of both sets of speakers.