I need advice and guidance for our recently purchased home. Basically, it is a 3 story duplex with an apartment on the 1st floor and another on the 2nd and third. I am putting radiant in concrete on the 1st floor (demo is complete) and radiant under the old red oak flooring (aluminum in joist bays) on the second and third. I have NG supply for both. I would like to put in separate smaller space saving combo units to run the respective single bathrooms and radiant floor systems. I prefer simplicity over technology. Total heating square footage is 1800, 550/700/550 on each respective floor.