If it where me I would go with the Onkyo receiver or one of the NAD amps if the speaker had a difficult load.
I'm not trying to be sarcastic here, but why? It seems you believe all decent amps are the same. If I felt that way, I'd recommend going with whatever had the looks and features at the right price the OP wanted, and the ability to drive 4 ohm loads is fairly common with most of the better makes, which wouldn't be an issue for many people even if they couldn't.
You are are truly over thinking this in my opinion. You need to figure out and firm up how much you want to spend and go with whats available in that price range.
I can agree with this.
I don't agree because there have been scientific double blind tests to prove that all well made solid state amps when operating within there specs and not clipping; sound the same. If the amps being compared are not level matched to within .1 db then the louder amps will tend sound different and more often then not be chosen as the better amp. No disrespect but your comparison of amps has no merit unless done under blind level matched conditions.
Not having participated in a blind test myself (I would love to), I have questions...
Were the people involved highly interested in audio? Under what conditions are the tests done under? Did they really like or know the music they were hearing? What kind of mood were they in? Were they comfortable/nervous? Did they spend prolonged periods getting to know the amps? Have you ever taken the test yourself?
What do you consider a "well made amp". If the amp sections sounded the same, what about the performance of other things like tuners, or balanced connections, special buffered inputs, etc. How about a perfectly working quality vintage solid state amp compared to an equivalent new one? What about an opposite extreme like some Apex amp vs. a high-end Bryston or something?
And why do some tell me that all audible electronics supposedly sound the same when all visual electronics or many other things in the consumer have obvious differences? Have we perfected something (audio) to a degree that any half way decent manufacturer using different parts/methods can always achive the same results? That would be a first for humanity!
There are so many variables I question whether tests like this really tell the whole story, and the OP's comparisons of amps may have no merit (if true) in some cold, calculated scientific way on paper, but they may to the OP himself. If he feels good about the component and he THINKS it sounds better, then it does sound better!
That is what's really important.