Depends on the size of your room, how loud you listen and how much power you want/need. Given that B&W is a challenging load with a forward sound profile, a warmer amp that handles lower impedances would be ideal.
For lower power I would look at Naim, for higher power I would look at AVM. These two brands match well with B&W, Focal, Magico, etc... where you have challenging loads in terms of impedance and need a warmer sound profile.
For lower power I would look at Naim, for higher power I would look at AVM. These two brands match well with B&W, Focal, Magico, etc... where you have challenging loads in terms of impedance and need a warmer sound profile.