Perhaps, but the difference are "over-rated" if they exist at all.
I guess the question now playing is this... are there differences with playing an audio track with the same source and speakers using different receivers/amp setups? SPL isn't always the most important thing because, I for one, like to keep my ears a little bit longer. Is there different imaging between different components? Don't people say that Yamaha receivers are a bit more bright? Is this what ShakyDeal is trying to get at? Is he saying that he prefers the nature of the sound that he's getting with his components? What's really happening at normal listening volumes?
First off, when doing a comparison like you're suggesting, volume levels should be matched for all samples. Human nature dictates that one will feel that a louder sample will sound "better" than a lower level one, even if the difference is barely perceptible.
Second, consider that the main differences we hear are on both extremes of the signal chain, not the amp itself. My tale is that once levels are matched, and all else stays the same, one would be hard pressed to tell one from the other, as long as everything is operating within their limits. I think this was touched on before.
This "wipes the floor" bit is based purely on non-scientific "testing" and reminds me of the great Ford/Chevy debates I lived with in junior high school. It's amazing how quickly these tremendous differences evaporate like the morning dew in the early sunlight when the criteria set forth are met and the actual items under test are not known to the subject.
As for tubes, well, some just prefer their music with a touch of even-order harmonics thrown in to smear it just a bit. ...kinda like slathering a fine porterhouse with steak sauce but, hey, it's their steak, not mine. ..just don't try to tell me that it "enhances" the taste of it instead of hiding it.
Remember, I'm talking straight music with no additional processing involved. Additional signal processing adds it's own devils but with HT processors, that's part of that beast. Here, there is no right or wrong: It's all personal preference, much like one preferring blondes, brunettes, or redheads.
But, I can't recall an AVR that doesn't allow NOT using them. (triple negative??)