I upgraded from a NAD integrated in steps. The Quads love power. I suggest that you find a used Parasound A21 used on audiogon.com and use the pre-out from the integrated to connect the A21. What I mean is - use the NAD as preamplifier and A21 as power amp. The first 10 Watts of Class A from Parasound will mesmerize you, if the NAD made you ecstatic :-) I started with the upgrade by using the NAD as power amp, with the TVC as preamp.
One more point - the Quads require a bit of toe-in. Try to use a equilateral triangle setup and you will be amazed by the setup with these Quads. Good luck.
One more point - the Quads require a bit of toe-in. Try to use a equilateral triangle setup and you will be amazed by the setup with these Quads. Good luck.