I've used Heresy and Heresy II with a Fisher 500B with pleasing results and am a huge fan of Klipsch Heritage speakers.
There are a couple of thoughts that come to mind.
First, it is likely with vintage Heresy's being over 20 years old the crossover caps have drifted off spec and become resistive. This can make for some rough sound. The good news is that it is not an expensive proposition to return the crossovers, essentially, to factory spec. No boutique caps needed. I was astonished with the improvement in sound that recapping vintage crossovers yielded in my LaScalas and Khorns. One source, Bob Crites has these caps on Ebay.
The second thing, if the Heresy's still sound forward, is to drop the midrange one tap on the autotransformer. This will lower the output of the K-55 by 3db. In some rooms I have found this to be a helpful change on Heritage crossovers and it's easily done and reversible.