Contrary to the audio theorists I think the AHB2 sounds better in mono. Though mono is worse in 2 Ohm than in stereo. So it depends on your speakers current demand. Hopefully, it does not lounge around in the 2 Ohm region.
The AHB2 is not bright, but if you have anything bright before or after it then you will hear brightness.
I paired my bright RAAL SR1a headphones with the a single AHB2 and Schitt Freya+ tube amp (4 tubes). That worked very well without fatigue. My solid state CODA 07x preamp with the AHB2 was not able to tame the brightness of the SR1a.
My office system is the following (2-channel and headphone with 2 sets of amps):
- KEF LS50 Meta + KEF KC62 sub
- Benchmark AHB2 mono
- CODA 07x preamp (smooth)
- Musetec 005 DAC (smooth)
- Audience FrontRow speaker cable with SpeakON termination
I like my Benchmark LA4 preamp better than the CODA 07x. It has more details on top. However, my 2 channel system is also a RAAL SR1a headphone system and the LA4 with the SR1a is a no no. (too bright). The CODA tames that nicely when used with the very smooth KRELL Duo 175XD amp.
I turn off one amp when using the other amps system.
Benchmark has a 30-day home trial period so it is a no brainer to ty it out.