Sorry for the super late reply! Didn't check back in...I was using a single 890 for about 2 years and then moved to a monoblock configuration when I got my Marten Bird 2 speakers little over a year ago. A single 890 was outstanding, but monoblocks is just like moving from a twin turbo v6 engine to a V12. Utterly effortless. I am super happy with this configuration...dynamics, transient response, richness, superb bass...all TdP hallmarks. Using EI KT90 in both amps.
How do u like your EAR 912 and Zesto Bia 120 configuration?? I've heard the combo before at Bob Levi's home and it was great!