The center speaker should be rated higher then the other satellites, but does not need to be as high as the woofer. In a typical 50 watt system , the bass speakers are 50 watts, the center around 25 and the sat's around 10. *This info is not necessarily textbook but intended to help get you started.*

Ideally all three front channel speakers should be identical or at least have similar sound characteristics so when (let's say) a plane flies across the screen it it sound the same from left to right (or right to left). The surround channels could also be the same. Alot of (the better)manufactuers market lines of speakers with similar componants so they sound the same. Nothing worse than the center channel having diff'rent tonal characteristics than the front left/right speakers. And for that matter the fronts and rears not sounding alike.

Size is pretty much irrelevant. Power-handling capacity should be equal to the other front channels. Quality is most critical. It is particularly important that the centre channel reproduce speech intelligibly. Some studios mix *all* of the film dialog into the centre channel. Even if they don't, most of the dialog tends to occur in the centre channel anyways. Auditioning a centre-channel speaker should involve listening to both male and female sources. The listener should also move to different locations when doing this. Most centre-channel speakers sound best if you are sitting directly in front of them. Since many listeners sit at the end of the sofa or in the armchair to the side, you must check the off-axis sound quality. Most centre-channel speakers use a three-speaker arrangement (or something similar in concept). There is a high-frequncy driver in the centre, flanked by a pair of low-mid drivers. This design is prone to a phenomenon known as 'lobing'. The interaction between the speakers causes variations in the sound level as you move off-axis and as the frequency changes. Lobing is usually most severe in the upper mid frequencies. This can have a significant effect on the intelligibility of the speech. Lobing has little impact if the speakers are aligned vertically, since you rarely listen to music with you head on the floor, ten feet away. However, when they are horizontal and you are at the end of the sofa, you may experience a substantial reduction in sound quality and find it more difficult to understand what people are saying. There are two ways you can check for this: look at published on- and off-axis frequency response specifications for the speaker or by listening. Manufacturers usually don't publish the sort of information you need to assess their products. Some audio magazines perform such testing and present the results in their publications. This lack of information generally means you need to do a listening test of your own - something which you should do anyways. Don't just plop down right in front of the speaker and give a listen to something flashy for two minutes - move around and see if it is as good in other locations where people will be seated. Take your own sample material for testing; a CD of well-recorded female voice is ideal (a soprano vocalist or a jazz singer works well). Take you time doing this, don't rush it. If the sales clerk tries to tell you you don't need to do it or tries to rush you, take your business elsewhere.