To give you the best balance of power and performance, select an amplifier or receiver that delivers continuous watts (many times also referred to as “RMS”) in accordance with the speaker’s continuous power handling rating.
For example, a Klipsch RP-8000F is a floorstanding speaker with a nominal impedance of 8 Ohms, rated at 150 Watts continuously. So, any receiver or amplifier that delivers right around 150W per channel at 8 Ohms with full frequency bandwidth (20Hz - 20,000Hz) would be a good match.
However, don't be misled; although a speaker’s peak power rating can be much higher (in the RP-8000F, for example, it's 600 watts), remember that peak power means exactly that…a momentary exposure. Trying to make any speaker perform for more than an instant at peak power is an open invitation for damage.
The right amplifier, one that has it's power well-matched to the speakers, will also eliminate the need to overdrive components (play them too loud). Which, over-driving can cause clipping, which distorts the signal and can cause serious damage to the tweeter or possibly even the woofer.
In addition, believe it or not, under-powering speakers can cause as much risk for damage as too much power can. For example, if listening to an under-powered system at a loud volume, you will be running a high risk of damaging or blowing the tweeter(s) altogether. So, just make sure your receiver/amp's power output rating is right around what the speaker's continuous power rating is.
If you have multiple speakers in your system, all with different power ratings, then you will want to gauge the receiver's output power rating based off of the highest-powered speaker in your system. This will usually be your Front Left, Front Right or possibly even your Center channel speaker.
Horn-driven speakers, such as Klipsch, are much more efficient than their direct radiating counterparts and require less power to create great sound. Just be sure to keep the receiver’s output closely matched to speaker specifications to ensure years of trouble-free performance.