Wow, nice deal on that Cambridge.
I would consider a few things. Firstly, I'd opt to use the sub's bass mgmt, if it has it has hi-level input/output. The link says hi level input... but nothing about output... (you know, applying xover, then sending hi pass to speakers...).
Then, Id find out what died in the NAD. If its just the amp section....
at the risk of giving you bad advice... you could use its pre/pro section to feed a cheap pro amp. I'd make sure with others if that's OK.
Otherwise, without knowing any better, I'd bet those linked integrateds by rnatalli are as good as the 3020, if not better. OTOH, NADs entry level integrateds aren't anything to write home about; they start to take off with their heavier outboard amps...