I had this sub in my system for a while and I found it to have good output, but not deep extension. I had it in a very large room and I did not have any issues with it straining except with really extreme levels. It is picky about placement too.
Is it calibrated? You should start with the sub at about 50% gain and calibrate with it set that way, then adjust between the two to achieve proper levels, not starting with 100% gain.