You don't actually use all the power an amp can produce in excess of what your speakers can handle according to the manufacturer. So having too much power, is like having a 450 HP engine in your car, knowing the speed limits in your area would have you barely touching all the juice the car has. When it's needed however, it is wonderful to have. I think the Kefs may be a current hungry design regardless of their wattage recommendations, the minimal impedance is important. They weren't current or power hungry in their early designs, esp. examples that Nud Fried helped design, years ago.
The real problem comes down to what kind of sound do you want. The W4S is class D I think . I have never loved any product so far with that class of power. I have heard Naim and if your budget will accept their amps I would consider them very seriously, but you should really try to audition them yourself. Did you mention a budget?
