It must be sales trickery! Right?
Most people abandon the fact that the amplifier you use is one of the most important things you need when driving a speaker.
I am going to use an example:
I had a client coming in on a Sunday, eager to buy a Monitor Audio Bronze floorstander, but after hearing the Monitor Audio RX8, he committed to the superior Silver range from Monitor Audio. The demo was done on a Rotel Pre/Power 200watts combination, which blew him away. Upon asking what electronics he has, he assured me that his Yamaha will do the trick, as the speaker's rated 150watts is way below his Yamaha's "rated" 180 watts per channel.
a Few days later, I got a call, the client says the speakers does not nearly sound as good as it did during the demonstration, can I help? So I jumped into the van, armed with the same Rotel Pre/Power combo, Audioquest Interconnects, Audioquest custom made speaker cables with banana plugs. Arriving at the client, I quickly added the Power Amp to the existing Yamaha's pre-outs. Magic happened, the client was ecstatic. I proceded by then using the Rotel Pre-amplifier and cabling, where the sound just opened up so much more. Needless to say, the client upgraded to the better, newer and more powerful system, and was happy.
SO, WHAT THE WATTS IS GOING ON?
So I am not going to bore you with the technical explanations, it is time-consuming, it is debatable, it is always being challenged, so here I will follow with the easiest way to explain it.
You have a Hyundai rated at 140kw, and a Mercedes rated at 140kw. Who will win the race? Same power right? But do we take into account weight, efficiencies, using more low-cost manufacturing components vs newer technology? Mercedes will always win, it just does it better, with the same rated power. You might add, the Mercedes has more torque...which makes for the next paragraph.
You never walk into an audio shop and asks for the most powerful Wattifier. You ask for an Amplifier, which produces amps, which is the actual electrical current driving the motors in your speakers, which produces watts.
Why the watts then?
Mostly marketing really! Thank you Sony PMPO.
So how do I choose?
There is no better way to choose the right amp for the right speakers, then going for an auditioning at your local showroom. Contact your local importer of the speaker brand you have, and ask them what they would recommend.
Example, KEF would most of the times recommend you look into Primare, which powers their speakers exceptionally well. Primare also powers most British speakers very well, including B&W and Monitor Audio.
Another example will be Yamaha driving Bowers and Wilkins very well, but not KEF as much, as KEF tends to be very sharp on the higher frequencies when coupled with a Yamaha, which is naturally a sharper sounding amplifier, which is once again neutralized by the B&W's warm sound.
You would find a Focal Speaker will not work at all with Primare or Class D amplifiers, yet, enjoys Class A and AB amplifiers from McIntosh and Marantz/Denon.
Go and audition, don't just read about it, it is much more fun!