How is going from NAD to Audio Refinement or Accurus even an upgrade?? These are all budget components and are not much of an upgrade at all. Since the electronics in these systems are hardly being upgraded, I can see why these posters think the speaker should be first.
If you spend $1500 on a used preamp and amplifier (like Conrad Johnson, Bryston, McCormack, Rogue, Blue Circle, etc, they will be at least two or three full steps above the NAD in quality; and you will then find your speakers are fine for now.