@bholler, if i was you i will be installing back the regency. Why to wait? If in the 30s is not performing any different than your regency and actually is giving you less output, why to wait for the worse part of the cold weather arrives. I do love my BKs but if one day they dont do what i want and there is something else that will do it, I tell you what, bye bye BKs. They will go to my collection spot in the back yard or for sale. My house is around 2400sf and really old, in the 30s i just run one of them and as long as during the day the temp climb outside a little i have no problem keeping the house at comfortable temp.
My technique is to load as late as i can before bed, burn hot and dial it down. By morning everything still acceptable. between 72 and 65 the upper level. I just dont do anything, anyway i am going to work. as long the sun shows up during the day i can find the house better that what it was when i left in AM temp wise. In the 20s and teens as have been lately i run both real low.