Do the tubes have to be matched?

I have a pair of ASL wave-8 mono blocks. Each one takes a pair of 6bm8 tubes. Right now i use 2 sets of matched Svetlana. I can get some nos Sylvania from a local electric supply house. But they have no way to match them or even test them to see if they work. At $28.00 each i wonder if it's worth it to get them. I have found there aren't that many choices of this style tube available even on the web. By the way these amps are auto bias. Thanks for your help.

Tommy