BEST POWER AMP OR INTEGRATED AMP FOR HERESY 3

And that NAD doesn't get it loud enough for you? Frankly, you'd better back it down a bit or this is going to be one very short-lived hobby for you...

-RW-

From my experience in MOST of cases tubes + Heresy 3 = hiss or noise. Very efficient speakers might be jeopardised by noise from tubes. The best bet is to go to class A SS amps such as used Pass Aleph 3. It may be less powerful than your current NAD, but the loudness from your speakers won't be compromised at all + you get the matching speed and thorough accuracy of class A amp to your speakers. It's also crucial to service the amp with new DC caps if it hasn't been done as they're the culprit of noise in both solid states and tube components.

You will want a quiet amp and one that is warm sounding to help amelioriate the brassiness of the midrange horn. McIntosh has a very curious synergy with Klipsch. Accuphase would also make a nice match.

I have used tubes with the klipsch Quartet which is 97.5db eff.

One was a primaluna with el34's and 35wpc and the other an vista audio i84 15wpc

no hiss on either one just sweet tubes and horns sound

Up until a couple years ago, I used a NAD C372 with the original Heresy speakers (which isn't all that different from what you have), and I could crank it up well above where I'd ever care to listen. I think RW is right!