The problem I see with a two tank system is you still have losses from the second tank and while it will boot the temp from the buffer tank it will still have to fire up ocasionally to make up for its losses.
I have a single 50 gallon on my 3 ton Envision but also have a remote control on the water heater. The water is hot enough to take a shower with but will run out as I only open the hot valve. So I turn it on right before I step in and it will actually get hotter during my shower. I turn it off when it gets too hot and before I finish my shower. In the winter I can leave the water heater off for about three months.