According to the "audiofool"’s the Aegir does not seem to suffer much from bridging.It is only 20w, "he talks about bass driving" and says "seem".
It was probably stressed in stereo mode and bridged just gave him more ooph!
There is no magic way of bridging an amp without the pitfalls.
Better comparison would have been on >100db speakers. then the stereo would surely have shone through.
Cheers George