rear surround vs. regular surround in 6.1 channel setup?

[stevos2005]

In a 6.1 (or 7.1 channel setup) that includes a rear surround channel in addition to the left and right surrounds, is there generally more sound in the left and right surround channels than in the center surround, or vice versa. What I mean is that, say, there's a 7.1 channel setup, should the rear surround and side surround speakers be the same pair, or should preference be given to spend slightly more on either surround.

Thanks!

[Sir Terrence the Terrible]

It is adviseable that the side and rear surrounds be of simular timbre. Since these speakers are alot closer together than your fronts, timbre mismatching will be a lot more noticeable as sounds are panned from speaker to speaker.