From my experience the AHB2 should not be used with speakers that go into 2 Ohm and I feel it does not provide thunderous power with speakers it even matches well with. When I demoed the Magico A3 speaker I took along a single AHB2 stereo amp and it was awful with the A3. A Mark Levinson amp and ML 585 integrated was so much better. I attributed the AHB2's poor showing to a lack of power.
Running the amps in mono are actually not rated for 2 Ohm while the single stereo is officially rated for continuous operation in 2 Ohm. I had monos on my hard to drive Thiel CS3.7 and it was lacking grunt. The CODA #8 and the KRELL XD line were so much better in the thunder department. The D-Sonic also had way more grunt than the AHB2 though I thought the AHB2 was the cleanest and nicest sounding on the Thiel (minus the grunt on certain music).
What I use the AHB2 monos today is really a killer setup. I have the KEF LS50 Meta + KEF KC62 sub in my small office powered by the AHB2s. I had planned on buying the Yamaha NS3000 monitors (almost $10K) from Canada but the AHB2 and KEF LS50 Meta sounded so good I decided to save my money.
I am done in the office system.
My Livingroom system which will be rather costly will either use the Benchmark LA4 preamp or Holo Serene preamp (both ASR wet dreams).
The following post on ASR about the AHB2 was so right on the money and so well written.
Review and Measurements of Benchmark AHB2 Amp | Page 5 | Audio Science Review (ASR) Forum