Tuck08

I'm sure this question has been asked a million times - How important is it to match speakers in a surround system? I'm in the process of putting this system together and currently have the following: Onkyo tx sr 805 receiver / Klipsch sub 10 / Klipsch ss-1 rears. I'm looking to purchase fronts and centers ( 6.1 system ) next and looking for advice - Synergy or Reference . Thanks to anyone with input.