vandersteen quatro with Naim ???

I don't think it will work, you need to get an unbalanced crossover with RCA connections. The XLR balanced crossover is different inside from the RCA unbalanced crossover for the Quattro/5A since it needs to work for both signals of a balanced system.

Go to the Vandersteen website, there is an extensive question/answer section. It should be addressed there. Or you could call them.

I know I can't use an unbalanced crossover with my balanced system, but maybe one could adapters for a balanced crossover in an unbalanced system, but I doubt it.
Terry

You need an integrated or separates with ((pre amp out)) either RCA or XLR and ((Main in))
You also need the Main in Amps input imp above 10 k to get your minus 3DB down point to adjust at 100 HZ for the Bi amp to operate properly.
Most all equipment separates can do this and any Integrated
with the above also.
Cheers John