A calc does not replace a feat, and should be used to show how impressive a feat is (not to inflate something or downplay something). Multiple people calcing the same feat to have results roughly in the same area, even if the energy result varies by even orders of magnitude would show that it's impressive. If an earthquake calc is done on three sites by three calcs, with yields in the megatons, gigatons and petatons depending on the methods used would all show this feat is impressive. This also may just be how I feel about it, but I also feel that levels of energy would not be restricted by their yield to the DC scale (for instance, a 900 kiloton explosion would be well past town level). Also on a similar note, being unquantifiable is not the same as being unimpressive.
