I have LS-50s as my primary speakers. the 'body-hugging Ferrari sports seat' analogy is not far off. If your room placement can accommodate them, the Magnepan .7 is everything you are asking for. and will not leave you feel like you have compromised. With lesser box speakers than the LS-50 (and that's most all of them) you will rapidly become annoyed with box colorations that simply don't exist with the LS-50 or the Maggie .7s. The .7s, on the other hand, will provide you a transparent and large window that is a very different, but equally enjoyable, listening experience.
If your NAD amp will drive the LS-50s to your satisfaction, it will handle the ,7s as well.
My second recommendation, only if placement limitations preclude using the Maggies, would be the KEF R3. Think of that as the luxury GT version of the uncompromised sports car that is the LS-50. A little bigger, a little softer, but definitely cut from the same cloth. And in this case with another 1/2 octave or so of quite noticeable bass. A warmer, more forgiving speaker than the LS-50, for sure.
And I have to laugh at the Heresy recommendation. The most gawdawful speaker I've ever heard, No low bass, squawky,honky mids and harsh tweeters. Yes, they are efficient, and yes a good tube amp can tame them to some extent. I've always wanted to like them for their dynamics, but in 50 years of listening to several versions of them, on all kinds of amps, SS and tube, I've never heard them sound even good. The only Klipschs I've heard sound good sound were far bigger and in a very large room. That seemst to be their place.