I don't know about the MRX720, the MRX740/1140 did measure very well on the bench (by Gene, Audioholics.com) and I assume you have read it.
I could not find any measurements on the PVA7, so I have no idea how someone knew it had "a better amp" and obviously that could be wrong, or right. Many people would assume a power amp must have "better amp" that those built into an AVR, that's a reasonable assumption, but again, based on specs and available collaborative information of the likes of the MRX720/1120 740/1140, the PVA amps are just comparable with no evidence of them being "better", when used with the front speakers only.
Either way, I am 100% confident that you wouldn't hear a difference if you don't know which one is powering the front 3 speakers. The PVA amp might have better continuous rating but we should know that continuous ratings are, in most cases not relevant to listening to real world contents, as movie and music contents are not pure tones, such as 1000 Hz, 2000 Hz etc sinewave tones. So, whatever is convenient to you, is probably the "better" way.
Regardless, the PVA amps, imo, are good for the surround/height channels, but in order to get the best out of the 936 if you listen to relatively high spl, I would recommend something like the MCA325 for the LCR, though for better value, something like the Hypex NC502MP class D amps or the Monolith might be better choices.
If you listen to spl at leat 10 dB below reference , then you don't need those "real
Learn about your DOTS score " 4 ohm rated power amps.