should I match old speakers with new ones?

The most important component to match with the front left and front right speakers is the center speaker. I would buy the matching center speaker from the same manufacturer. I would not worry about matching the front three with the rear surrounds nearly as much.

I often find better surround speakers for less money, usually made specifically to be surrounds, from different manufacturers than the front LCR speakers I've owned. Calibration has never been an issue either. I've had no trouble fitting in different surrounds in with a system.

depends on how OLD r they ??

i say if u r going to get NEW speakers try them separate and compare the sound quality by EAR