Do your speakers go into 2 Ohms territory a lot? If not, then a single AHB2 would work incredible with the HPA4. You could always add a second AHB2 to run as monos. I do that but my current speakers, KEF LS50, they do not require monos (overkill).
I like the AHB2 over all other amps I have had with the HPA4. I also like the AHB2 over way more costly amps. I just love the sound of the AHB2. Here is a list of amps I remember trying with the HPA4:
- CODA #8
- D-Sonic M3a 800s (Class D)
- LSA Voyager 350 GAN (Class D)
I think you can do a 30-day home trial with both amps you are considering.