You should always get a amp that can deliver a little more than the max wattage suggested by the manufacturer. Please read my other post where I have explained the reasons in terms of SPL, distance, and wattage required.
Speaker manufacturers use specialized rooms for testing. These room have 0db noise. Really zero db. No one sits inside the room, and sound levels are measured at various distances under controlled circumstances. There is nothing disturbing the sound as it travels from the speaker to the highly sensitive
mike.
In the real world your room is never quiet. There is at least 20db of peripheral noise at all times. Thus those specs have no value in the real world. You have to add at least 50% more power in the real world.
B&W are different. They use Kevlar for the drivers. Kevlar is hard to move. If you pump 25-30 watts to the 600s, it wont even wake up.
Cheers
Thanks ! Have come across few links explaining the terms
Loudspeaker Sensitivity and Amplifier Power Requirement
Crown Audio - Professional Power Amplifiers
Sound Pressure - recommended Maximum Level in Rooms