EAR 859 - Opinions Needed

Does anyone have any opinions on the EAR 859 SET integrated amp?
I use one with the Tannoy Churchills excellent amp for high eff. speakers 90db+ eff. Excellent imagining and great detail.
Fabulous. I run mine into stacked (four of) Quad ESL57 electrostatics with fabulous results. All analogue source(s).

Problems? Might be I can detect a slight, very slight, mains hum...although I don't think it's in the signal path, just comes from me being close to the amp's transformers themselves.