It seems strange to me that two amps and the receiver are all defective at the same time.
Are you sure that replacing those amps is wise? Although those speakers measure well, they are in my view a "Mickey Mouse" design. The fundamental problem is the the amp is powered from a speaker output. I also have integrated main speakers, that also capture the LFE channel. However I used a much more robust and professional design approach. Those speakers could be significantly improved in my view, if you used two power amps and a fourth order electronic crossover at 150 Hz, which is the same order your speakers use. Then connect an amp to the bass section. Take out the low pass section of the passive crossover to the mids and leave the top end of the band pass section and the high pass filter to the tweeter. Then you connect the top end amp, to the top end of the band pass and high pass crossovers. Then build a simple mixer circuit to add the LFE channel to the bass amps.
I'm not really a receiver guy, and use Marantz pre/pros. If you really have had failure of your speaker amps and the receiver, then one or the other blew up the other.
So I would regard this as an unstable situation. Using a speaker output to power an amp, is not an optimal situation. Definitely it is not something I would do personally.