Either will surely please. The SUR has a little more power but we are talking around a 1.5db difference; not that significant. I would also take a look at the differences between functions & features.

Lastly, if it were me, I would bug the hell out of the store owner/manager to get a SUR in stock so you could compare the SUR and NAD for yourself. I don't understand how any retail establishment can be a dealer of a certain brand yet not have any of their products available to demo. Do they really expect somebody to pay $3695 without giving it a listen first? Madness.