Not a very hot answer.....
From experience I can tell you that most any mainstream (Yamaha, Denon, Onkyo, HK, etc.) receiver sounds the same as the others at a given price point. In the upper upper end of the scale there can be a bit of a difference, but that is dependant on taste. To be a receiver connoisseur is like being the connoisseur of fast food. Is a Big Bacon Classic different than a Whopper? Well, yeah, but they are essentially the same thing (I prefer the Big Bacon Classic by the way) in the same market space. Anyone who tries to sell you on different is just trying to sell you on different. One year, one brand will have the fresh new hot product and technology, the next year it's another, and the year after that another. Flip a coin, then hold your breath.
Yamaha is the absolute KING of frilly nonsense on a receiver with all of the DSP modes (who actually uses all of those?) they throw on there. Keep in mind, though, that all of the mainstream brands have funky named proprietary processing of some sort.
I will tell you from extensive experience with both brands that you can straight up absolutely hear a difference between a $1000 THX Select Onkyo and an entry level $800 NAD. The NAD product sounds a lot better and is $200 less... on the surface. While it has better sound than the Onkyo, you know what it doesn't have? HDMI switching, up-converting to component video (it only has 2 component video inputs) from composite or s-vid, THX certification, and a lot of marketing dollars behind it. That's why I said that it's cheaper... on the surface. Take that stuff away from the Onkyo and I guarantee you its price point plummets down past the NAD. Two companies competing with two different sets of values. And neither of them is wrong, really. It just comes down to what you need/want in a product.
By the way, while I like NAD and recommend it to people looking only for high end sound out of a receiver on a budget; I usually sell Marantz receivers to my customers. I think they offer the best compromise between great sound, price, and features like HDMI switching. As for separates are concerned, I don't do NAD anymore because I hate making customers pay for inferior video switching. I use Parasound, which most models don't have video switching, and sell the customer a nice video scaling product.
Bottom line, you can't go wrong with any of the brands you listed. Pick the one that fits your budget the best and enjoy.