I'm a huge fan of auto calibration on receivers to help out with some of these issues. MCAAC has made a world of difference in my living room. I'm assuming that have, but I'll ask...have you run the calibration on your NAD?
Unlike many NAD products, this one doesn't appear to use Audyssey, well not any version of MultEQ anyway.
That said, it's still very hard for me to believe you can't auto calibrate for two speakers only. Though the results will probably be minimal, it's a single position calibration.
The move to the new house was a really good lesson on the importance of room acoustics. The floorstanders I use for HT sounded awesome in our previous home and crummy in our new (old) house. The bookshelf speakers I use for music playback sounded pretty bad in our previous house because the room was too simply too small and sound great in our new (old) house.
The next residence, if ever there is one, and the daughter is still there, beat her to the punch by singing, shouting, clapping, yelling, having wild sex, in every room before they get dedicated to whatever purpose. You'd be surprised at what you can get from a single shout, even if having the whole setup might be more indicative of the situation, there is IMO a lot to get from simple testing like that.
All that aside, there are only a couple of small things that cross my mind. The first is only for a really cuckoo audioholic, but when no one is around, start putting the speakers and yourself, in all sorts of positions, I'm talking even the most ugly, unacceptable, useless positions. You might be surprised with a certain positioning, and at least you'll know where to gravitate towards, if willing to move stuff around for critical listening. I've in the past recommended sliders on couch and stuff for this kind of thing.
The other thought is that, yeah, it's sure possible that every speaker you buy will be displeasing to you, so the only way I see is being somewhat of an abusive customer, by purchasing bunches of speakers that allow for 100% return within however many days, and spending the time to listen to them in room.
Outside of the above, given your stated circumstances, I can't think of anything else atm.