We are debating between two inserts - the Enviro Empress and the Harman Accentra. We like the looks of the Empress better, but my main concern is heat output. I want the one that puts out the most heat. The Empress USED to say it was 40,000 BTU input. (I have last year's brochure.) Now they claim 34,000 versus the Harman's 42,000. The weird thing is that the Harman claims to heat about the same square feet as the Empress. So a couple of questions... 1) I assume that the square foot figure isn't reliable at all. Different manufacturers make different assumptions. Is this true? 2) Why did Enviro reduce the BTUs of the Empress? Was it calculated wrong to being with? 3) Which stove is the most efficient. Incoming BTUs mean little. It's outgoing that matter. Is there a more efficient insert than either the Empress of the Harman? 4) What is the advantage of a gravity feed system? I know the advantage of Harman's push-type auger, but I haven't heard what the advantages are of dropping the pellets into the combustion area. Thanks!