I would not be so worried about getting new output tubes that supposedly come closely matched. When you set the bias for the tubes in your amp, you are in a sense "matching" the output for all the tubes yourself. Autobias amps do it for you automatically. This makes the output of each tube very close to equal. I would be more worried about getting a good match on the input or driver tubes for the amp, which make more of a difference in balance. Those tubes are not usually in a circuit that is automatically or manually biased. Also, as Lostbears stated above, brand new tubes need to be burned in for a good while before you can get a stable reading on how closely matched their output is. Some of the big tube dealers mentioned above charge a LOT of extra money for "matching" of new tubes. I have personally tested quite a few pairs of "platinum matched" tubes right out of the box, on my Amplitrex AT1000, which were off by as much as 35% on their GM readings! Needless to say, they got sent back for a refund immediately. I later ordered the same tubes new from a China dealer on E-Bay for half the price, and they tested within 5% of each other and very strong when they arrived.
Audiophiles don't need to be so fussy about tubes who's readings "match" so closely. Your ears will never hear the difference between a pair of tubes that match within 3% of each other or a pair that are off by 10%, especially when they both test very strong.
