We do seem to get complaints about failures of Anthem equipment here more often than I would have thought we would considering market share. However these factors are hard to judge.
The bigger issue is your speakers. Unfortunately B & W speakers, as a group, tend to present a torture test to amplifiers. I don't know why B & W persist with this, but they do. It has seemed strange to me that B & W have produced so many speakers over the years, that have such off the wall impedance curves and phase angles.
This is a graph of the phase angles and impedance plot of your speakers.
Note that the impedance is around 3 ohms during much of the range where a lot of power is required. In addition the phase angle is a whopping -65 degrees at a point where the impedance is four ohms. That is just a horrible load, and close to a short circuit effectively at that point.
Now your STR amp does have a 2 ohm rating. However I suspect the amp is just not comfortable with the load presented by those speakers.
As say this as someone who has designed many speakers over the years, and have never had a design present a load anything like as horrific as the one above, and would not pass one that did. I just would expect trouble. John Atkinson in his review of those speakers commented on the fact, that that load would stress amplifiers, and so it will.
So having blown two of those amps, if you keep replacing them, you will keep blowing them driving those speakers.
It has often been commented that to drive many B & W speakers, you need an amp that can substitute as an arc welder!