I love Heresys, I messed around with a pair for a few years, wish I still had them. Initially I ran them with. Edenlake EL34 amp. It was much the same amp as the Icon Audio EL34. That was nice, a Manley Stingray was a big upgrade. Running in what was effectively a single-ended mode it made a lovely liquid sound with a huge amount of shove. Those speakers are like huge Linn Kans, the way they time is extraordinary. Then I had children. Hot glass bottles were banned, and in an effort to retain the fluidity of the valves I bought an expensive Shanling amp, that was all class A. It was ok, but all the magic had gone. I also heard some Heresy’s once on the end of an Avondaled 32/110, with an Avondale power supply. This was not a good thing! It was a complete mismatch.
I would seriously consider using Quad amps. A 303 would love it. Add a 34 pre-amp and it would sound great. I’ve heard that combination running big Tannoys and Tony’s La Scalas, it’s fantastic. I’d also consider a 306, but I suspect you don’t need the extra grunt it offers.
The little Tripath amp is fabulous also if it meets your needs. Passive pre-amps are great in the right context. I’d seriously consider trying to borrow a passive pre, or make one! Tony has one he built in a Tupperware tub! Then try a Quad 303 and the tripath options. See if they give you what you’re looking for. Also build the raisers. That makes a big difference to the sound.