Yes. Different power ratings don't really matter, since it is how the speakers are installed and used that counts. However, different power ratings suggests that the speakers are different, which may not be desirable. In addition, care should always be taken when adding more speakers to an existing audio system. If you install two different speakers for the left and right channels, for example, they will not sound the same. All speakers are slightly different and some are very different in sound. You should ensure that the sound quality, frequency range, and clarity from all speakers in a system is similar. This does not have to mean that the left+right and left+right surround speakers must be identical, but if they are quite dissimilar, you will notice it. If you add additional speakers into the circuit with an existing speaker, you must ensure that the combined impedance of the speakers is not too low. If two speakers are wired in parallel, their combined impedance is: 1/Resistance_Total = 1/Resistance_A + 1/Resistance_B If both are 8-ohn (nominal) speakers, wiring the pair in parallel will produce a 4 ohm (nominal) load. If one is 6 ohms and the other is 8, the combined total will be 3.4 ohms (1/R = 1/6 + 1/8). This is too low for many amplifiers. The reason that I keep stating nominal impedance is that the impedance of a speaker is not fixed, but varies with the frequency of the input signal. A speaker with an 8-ohm rating could very well present a load to the amplifier ranging from 4- to 50-ohms. You don't want to cut the speaker loading too fine with some amplifiers, because low impedances can adversely affect the sound quality. The upper and lower power rating (wattage) of any speaker must be taken into consideration. Speaker power ratings from many companies are unreliable and many companies inflate the ratings of their products, through questionable testing and measurement practices. More power sells, even if the speaker is not capable of it. If a speaker is connected to a low-power amplifier, even if it is above the minimum power rating of the speaker, you run a serious risk of damaging the speaker. This is because damage is most commonly caused by distortion, which increases sharply if the amplifier is pushed too hard. It is difficult to damage a speaker with too much power, but you should not use an amplifier that produces much more power than the speaker's RMS power rating. For example, the power amplifier on my main system produces about 125 watts per channel into an 8 ohm load. The recommended amplifier power for my speakers is 20 to 180 watts. So anything up to about 200 watts is a good match and experience tells me that 25 watts would be a bit of a strain. I could use an amplifier rated up to 250 watts safely, provided I did not party too hard with it on a regular basis.

It's best to use matching pairs for a more balanced sound. Higher Watts just means greater capacity, but watch the Ohms: too low puts a larger strain on the amplifier, too high and you may not get enough volume.