First of all, just a few bullet points:
- Hotel California does have some strong bass, quality of the recording is much more important than quality of amplifiers. Even my desktop system can produce satisfactory bass and there is no reason why the Yamaha RX-A8A could not deliver the bass in that recording. I have only ever own one Yamaha AVR but based on their specs and measurements, there is no way the MRX1140 can do better in bass.
@AcuDefTechGuy is experienced with Yamaha as he has their AVRs as well as an AVC, I am sure he will tell you his Yamaha units "sound" as good as his previously own separates, let alone AVRs of any brands.
- I would like to trust your findings that the MRX sounded so much better at higher volume, but the published specs and bench measurements simply did not support that at all. The X6700H and A8A you compared with the 1140 have very similar rated output into 8 and 4 ohms (within 1 dB or so..) under 2 channel driven conditions and the Denon did much better (still less than 2 dB or so..) in 5 or 7 channel conditions.
- If you search for users reviews you will find that any of the 3 units mentioned have their supporters who praised their "sound quality", such subjective reviews on forums are not reliable, almost meaningless in some ways. So who do we believe? The problem is, such reviews (especially those written by professional reviews) might have biased their users, who, combined with the effects of manufacturers marketing information would then have a preconceived notion that one of those on their initial short list would indeed "sound" as described by what they have previously read on the internet. Once that's (the preconceived..) there, any sighted tests would likely be meaningless.
- Unless I misunderstood some of your points, you seemed to have said that at lower spl, they didn't sound much different (if at all?), except at higher level (you mentioned reference level..), there was a big difference. If that's the case, I would say you were pushing the other units pass their clipping point and that would render such a test invalid because at such high level distortions could/would increase rapidly. You should have cranked the 1140 further and find out how many more click (usually 1 or 0.5 dB per click) on the volume dial would make the Anthem sounded bas too. That would at least tell us if Anthem has some sort of soft clipping feature and that may answer your question of why a similarly not more powerful unit could sound better than the other two at high output levels.
- I have not auditioned an Anthem unit recently but in the past I have compared two Denon AVRs with my separate preamp/amps (including an Anthem power amp) and there was no audible difference found in my comparison listening at low to moderately loud level. That's expected, based on specs and measurements, so again it is not that I don't believe your findings but if you too, must believe in science and engineering, so I think you would agree that there has to be some correlation between subjective and objective measurements. And if not, then it is time to find out what could have caused such significant discrepancies.
Anthem happens to be one audio manufacturers who, on the often hyped up "sound signature related myth" have stated the following in their FAQ section:
So as I mentioned before, if you actually heard such major difference in your comparison listening session then I think most of us who responded so far who like to hear back from on the following:
1) Did you listen in direct, or pure direct mode and make sure that there was no sound processing (including room corrections) in use?
2) Did you level match all of them to within 0.5 dB spl from your mlp?
3) Was the exact same media content and media player used?
4) Did you use the same interconnects and speaker cables (iirc, you did imply same speaker cables on banana plugs)?
5) As someone asked before, what's the time delay between switching from one AVR to the other? You did say 1 to 2 minutes, but would that be the total delay between one stop making sound to the other taking over and at the same level, that is, all adjustment time included?
If the answers to all of the above are affirmative, there shouldn't be much audible difference even if the tests were done sighted, and you would almost certainly be not discernible if the tests were done "blind".
Regardless, I agree with HD 100%, in the end you only have to convince yourself. So if you are convinced your findings were totally valid then you need to find some good reasons not to go with the MRX 1140, otherwise, as you said, go for it!
In reality though, between those 3 (6700, A8A, 1140), and objectively speaking only, the deciding factors appear to be features , perceived reliability and customer support based on track records. Trying to determine, or rationalize which one "sounds better", is, in my opinion, a waste of time, especially if based mainly on anecdotal findings from others or even your own, unless you are sure you did some truly apples to apples comparisons.
