I'm going to be blunt here. I wouldn't even consider driving the $19k Otellos with two channels of a seven channel amp or a prepro in the name of saving space, or anything else for that matter. To me, speakers of that caliber deserve their own good stereo amp and preamp (or at least a very good integrated). Buy a decent 3-channel amp and prepro to drive the HT, but I'd put as much as possible of the electronics budget toward the stereo components that get the most out of the Otellos. You can easily integrate the HT and stereo electronics into one seamless system, so operationally this setup works well and also allows you to spend more of your budget on the more critical stereo components.
Also, I'm still not clear. Are you considering having both the Otellos and Grand Pianos set up side by side at the same time? If so, that's an imaging nightmare and a big no no in my book. Personally I'd sell the Grand Pianos and just use the Otellos as front L/R speakers for both stereo and HT, or sell your rear speakers and put the GPs back there. Having heard both the Grand Pianos and various Verity models (awesome speakers BTW), my take is they're voiced similarly so this might work out well. Just my $0.02 FWIW, and best of luck in whatever you decide.
Also, I'm still not clear. Are you considering having both the Otellos and Grand Pianos set up side by side at the same time? If so, that's an imaging nightmare and a big no no in my book. Personally I'd sell the Grand Pianos and just use the Otellos as front L/R speakers for both stereo and HT, or sell your rear speakers and put the GPs back there. Having heard both the Grand Pianos and various Verity models (awesome speakers BTW), my take is they're voiced similarly so this might work out well. Just my $0.02 FWIW, and best of luck in whatever you decide.