I can say with 100% certainty that the Ref 110 is a better sounding amp over the HD 220. Audio Research Ref products are much different then the none Ref products. It's not even close...
Audio Research REF-110 vs. HD-220
I have a REF-3 and an ARC CD-7 and I'm planning on upgrading my ARC Classic 60 for either the REF-110 or the HD-220. I have efficient, full range speakers (92db Legacy Sig IIIs). My question is: have any posters here had the opportunity to have both amps in their systems long enough to be able to say what the differences are? I listen mostly to jazz, female vocals, light classical, classical guitars and some large orchestral music. Tonal accuracy is very important to me, as is the emotional impact of the music. I'm much more the music lover than the audiophile. Thanks ...