upgrade is back

[Pim]

But let me be VERY CLEAR, MORE POWER DOES NOT IMPROVE SOUND QUALITY!!!  It ONLY increases SPL, that's Sound Pressure Level, the ability to play at higher volumes and maintain the same level of sound quality.

My experience differs a little so let me tell you about it.
I bought a 170 with the idea that one day I would upgrade to larger speakers and I could use it as a pre-amp with more powerful mono amps. The the upgrade to 200 came along but with the extra power we also got SAM so I can't comment on the merits of the extra 30 Watts.
I got to like the sound of the 200 and also heard the 250 on Vivid Giya G3's and loved that sound so when the dual mono 800 was introduced I thought I might just stay with the brand and upgrade one day to an 800 for the extra power I might need.
Then came along the chance to buy an Original d' Atelier at a very good price. A very good price though for what the market value was but not a cheap buy for me at all. It was a LOT of money to me and I had to have a deep conversation with my wife about it. I bought it unheard with in the back of my mind that if it didn't live up to the hype, I could sell it on for what I paid for it or even make a little bit of profit on it. So we went ahead with the buy and soon we owned an amplifier that cost as much as a car! Crazy!
Anyway, we installed it and I listened. Keep in mind here that my speakers are only small and can't handle anywhere near the power the Od'A can deliver. They do like power though and that's where my experience differs from your theory. Where the Od'A pulled ahead of the 200 was not in SPL because I simply couldn't put all that power to use. It pulled ahead in low volume clarity and bass performance. And that was the only thing I had to make my judgement on. Higher SPL wasn't going to happen and I doubt with my speakers I'm my room at the time I could have picked the difference between the 200 and Od'A at say 85dB at the listening seat.
I know it's easy to say that the placebo effect would have altered the way I was listening but that simply isn't true. The difference in bass depth between SAM on and off is much bigger on the 200 than it is on the Od'A. I think that this is because of the Od'A's extra power or maybe it's because the Od'A is just the better amp. But it's definitely there. It's there so clearly, placebo effect is not even an option.
So there you have it. Same SPL, different amp. Different sound quality. 
Now, does this mean the upgrade was worth the money? Not if I stick with my current speakers and definitely not if I don't build a purpose built listening room. The differences aren't THAT huge. But they are definitely there and definitely will be worth it the when  I upgrade my speakers. As with everything, the law of diminishing returns comes into play. You don't get twice the quality for twice the money. A Volkswagen Golf GTI takes about twice as much time to get from 0 to 100 km/h as Porche 911 Turbo does yet the Porche costs about 8 times as much. That probably gives a fair comparison rate with the Od'A/200; 1.5 times as good for 4 times the money.
You mentioned you would probably rub people the wrong way by posting your theory. You don't rub me the wrong way at all. I'm a big boy and I know what I want in life and don't really care what others think. But what I do think is that you're a bit off the mark and maybe you should have a crack at listening to a higher dollar value Devialet amp in a good room with a good set of speakers, well setup and with a glass of your favourite plonk in your hand. You might just find you're wrong