How Important is Tube Matching?

I was wondering how important tube matching is for a preamplifier. I had read somewhere that tube matching is extremely important if the tubes were used in an amplifier but was less critical for the preamp. Is this true? I've recently acquired a tube preamp and want to upgrade the tubes but wasn't sure it was worthwhile to pay the big dollars to get matched set(s)...It's a six channel preamp! Any advice would be appreciated.
Thank you!
calgarian5355