You've got pretty good responses and I'll add a little of my own here. The ARcam ALpha 10 was my first integrated amp and having listened to the Alphas 8 & 9, the former is a better amp with greater dollops of power and refinement. However, I realized it was a bit of a cold fish after a while when I moved up the upgrade path. The Arcam was clearly lacking in dynamic swings when you needed it the most. Having said that, the ALpha 10 was still an excellent unit in some systems, and I believe it will be an improvement over your NAD.
Although I haven't listened to the Roksan Caspian, you might give it a consideration too as I've read it's a better-sounding amp than the Arcam.
Although I haven't listened to the Roksan Caspian, you might give it a consideration too as I've read it's a better-sounding amp than the Arcam.