The front three should be of the same make and line within that make. this helps assure a "timbre matched" sound in the front plane.

As for there surrounds, there are two schools of thought.

For HT, you can get away with different make/model of surrounds than the fromt three. It helps if they match each other though. This is because HT uses these for sound effects, ambient sounds and backgtound music. Matching the fronts isn't a show stopper.

For multi-channel music, however, I would recommended that they match the front speakers. Music is music.

As for the subwoofer, the brand used does not come into play here. You can match virtually any subwoofer with virtually any speaker setup. Generally, get the best subwoofer tou can afford. You can always turn it down but you can only turn it up so much.

Please note this may NOT be true in all cases such as with Bose and other "all in one" packages that have integral circuitry for the other speakers contained within them. A good clue that there may be problems here is if all speakers must be connected to the subwoofer.