From most accounts, I've heard that the Quad 12L is a better match for the NAD gear.
The Quad 11L is apparently a little forward sounding and better with more laid back gear such as with a Cambridge Audio setup.
If your budget will stretch to it, the warmer sounding Quad 12L is probably the better way to go.
Though, I haven't personally heard them. Just passing on what I've read so far. I still haven't decided between the Quad 12L and the B&W 602 S3s. Though, I think I will go for the Quads.
There is anyone who have already heard this combination?: Nad c352 with cambridge audio 640C, compared with, cambridge audio 640A with 640C. What is the diffrences between the 2 combination(i am meaning to the differences in the medium vocal and the details of the sound and the low bass )