There is no reason not to know the temp in the digital section. And letting the user control the temp digitally is what I meant by letting the µ-controller control the set points. The only thing I would off-load to the opamp circuits is the computational stuff. Let the opamps sit there and constantly (not just continuously) perform the "calculations" and exert the control. Use the µ-controller to communicate with the user, and to let the user communicate with the opamps.