I've seen a few posts about this combo and seems like it's the Heresy's themselves that people either like or not, but the amp should drive them to good volume since they have such great sensitivity.  

I've never had horns, but the size of your room may be a determing factor as I have read that horns need some distance between the speakers and listening position to really blossom and that a good subwoofer to pair the Heresy with is also generally needed, so a lot of people prefer the La Scala instead as it goes deeper.

I think they are very cool looking though and very retro, but I wish I could give you more advice about their sound.