Questions about speakers (sides/rears)

[robchow]

I am looking at upgrading my HITB speakers and have some questions about sides (in 5.1 environment) and rears (in 7.1 environment) speakers.

I have read that one should have the front/main and center speakers match timbre. Typical, this is done by purchasing the speakers (fronts and centers) within a manufacturer's series product line (i.e., Polk RTi, Klipsch Reference, etc).

I have read (and I can't seem to find it now) that matching sides speakers to the fronts are good if using it to listen to music. However, is it necessary (or good) to have matching sides/rears to the fronts for watching movies?

Thanks