Unless you did a properly controlled comparison (level matching, blinded listener, etc), then you could easily be swayed by the looks, price, and positive press for the NAD and be convinced it sounds better.
As for the comments about Denon and Marantz, well, it kinda proves the point. Their rep will tell you Marantz is better for music, sound quality, or some nonsense like that, and people will believe it. That's precisely what they want you to believe, because after all, Marantz products are priced higher. But then you look a little closer at the products and see that they're designed by the same team of hardware engineers and in many (most?) cases, they share the exact same hardware - except, of course, for the fancier looking Marantz front panel that somehow justifies the additional cost of Marantz and also somehow convinces some listeners that the Marantz sounds better.
As for your comments about NAD's power ratings, I do agree with you there. NAD tends to be conservative, and dare I say it, honest, while Denon, Marantz, Onkyo, Yamaha, et al, stretch the truth like it's a rubber band. But as I pointed out, the Denon 1712 - the AVR under discussion here - is more honestly rated than many others and more robust than many similarly priced receivers.
For every new thing I learn, I forget two things I used to know.