In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
I thought I'd post some pictures of my now-functioning system.
I have to give a big shout-out to the community here - I couldn't have done this without you guys.
We have warm floors, and the whole house is pretty warm, despite no radiators on the second floor, or in the basement, yet.
My original plan - to use the system sensor to control the boiler to keep the water at whatever the reset curve dictated - did not work. I had bridged the T-T, and the boiler kept overheating and locking out. I think it's because the alpha was only powered when the boiler was 'on'. I'm thinking that the alpha should have constant power - and the reset curve should be shallower - so the water is as cool as possible. I'm still experimenting. As I have it now, a t-stat in the living room is controlling a z55 upstream of one of the manifolds - that supplies 6 floor loops and 2 radiators on the main floor (very open space). I have the valve wired to TT, so that when the valve opens, the boiler fires and the boiler pump and the alpha are powered. No more lockouts.