@cbordian To answer your question without swaying you to keep amps or move to different one or two:
While cranking up the volume on your NAD may give you the adequate output gain and SPL overall, it may not have the overall headroom to handle the impedance curves of the Maggies and have a firm grip and full control of the speakers. Adding a second amp and going into monoblock configuration will be about driving the speakers more easily, with better control rather than added volume, and you will likely realize added speed, clarity, space and impact.
That said, at the end of the day, others are right that the NAD will only get you so far, so it's likely only a stepping stone (albeit likely a good one) before getting a different amp that can drive them exceptionally.