H2O Signature Stereo vs H20 Signature Mono Amps

I am in the process of downsizing my rig and am curious to learn more about the H2O amps.

Has anyone compared the signature version stereo amp to the signature version mono amps? If so, please share your findings in the comparing of the 2 set-ups?

Do the signature mono's perform that much better than the signature stereo to justify twice the price?

Is Henry coming out with a pre-amp? If anyone has info on this, please share what you know.

Are the H2O amps a fully balanced design?

I am strongly considering matching a good tube pre with solid state power amplification. If you have had success or failure doing so, with the H2O amps, please share your experiences.

Thanks!