You mentioned putting the sub in differing locations...How did you determine the locations to put the sub?
Have you done what is called the "sub crawl"? In simple terms, physically place the sub in the listening position, play a bass heavy selection (the menu from Godzilla works good as well as the beginning of Renegade by Styx) and then literally crawl around the perimeter of the room listening for the best bass response.
When you find the best "sounding" place (which may not be the best physical location), place the sub there and then re-calibrate. Make sure to note the other locations which have substantial bass response as the "best" location may not be feasible. Make sure to strive to get the phase right during calibration as that will detrimentally affect the "punch in the chest" sensation.
Another observation: What are the dimensions of the room the HT is in? Does the room open to other locations?
I have a SVS PB12-Plus/2 and it smokes the old subwhimper it replaced...this one even is better than the SVS 20-39 PC Plus I had previous to this one...I also purchased mine before the Axiom subs came into their heyday.
I tend to agree with everyone else that it is probably related to location and / or setup...That SVS should literally make the KLH whimper in fear.
Hope this helps.
"Meddle not in the affairs of Dragons, for you are crunchy and good with ketchup..."