I'd not consider the 1.7i as an option if you plan to keep the current NAD integrated. They will not sound as good as they are capable of. Also, depending on the size of the listening room, types of music, and the listening volume, the (stereo) Schiit Vidar may come short too but you could potentially grow them to monoblocs later.
I've owned the smaller Magnepan MMGs and currently own the large Vandersteen 2Ci and to me the Vandersteens sound a lot more balanced and closer to "real" music. But all these aside, you should listen to both and then decide for yourself. But when doing so, pay special attention to the partnering amplifiers used in the show room when you hear the Magnepans and consider their impact in your ultimate decision. The 1.7s will sound significantly better when driven by a very high power SS amplifier, likes of Mark Levinson, Krell, Bryston, etc. I think you'll find the1Ci sound a lot more natural and much more forgiving of the partnering gear.