I'm about to install 2 Rinnai R94LSi tankless water heaters (with a re-circulating system) to handle a new bathroom remodel I'm working on.
The new shower will have 4 Kohler water tiles (2.5GPM), a hand shower (2.5GPM) and an overhead shower (4GPM). The heaters will be used for the rest of house as well (1.5 other bathrooms, std stuff, 1 sink in kitchen, 1 washer, 1 dishwasher). The new shower will use the Kohler 3/4" Thermastatic valves (though considering the DTV system as well).

This forum has me paranoid that I"m making a huge mistake, though I don't know of any tank option to get the water flow to support such a shower. My current water heater (10yrs old) supplies enough water for my wife and I with our pre-remodel shower. It takes 2min for water to get from turn on in our kitchen currently, hence the want for the recirc system. We're having the units installed by a Rinnai authorized installer to prevent installation hassles.
I should note that we're in Texas. So things don't get overly cold.

Are there tank systems that support such a setup?
Spending all this money and ending up with a cold or fluctuating shower temp would drive me nuts.