I was recently jamming w/ one of the most seasoned & toneful players I know. When we got to talking amp-tone-shop afterwards, he acknowledged the importance of good power tubes in the mix, but TOTALLY dismissed the notion that whether power tubes matched or not could be important. I found it hard to argue against his empirical arguments (tho he'd a never termed them so): 1) most of the best, most coveted amps were produced & sold before anyone thought of tube matching & 2) they weren't coveted because of happenstance tube matches; 3) many of the most famous recordings of great tube amp tones were undoubtedly made with amps that were NOT using matched power tubes, because they were made before anyone ever thought about matching power tubes. I found it hard to argue with. But, afterwards, we went farther & did several double blind experiments with several musician friends with several amps, including those using 6L6, 6BQ5 & 6V6 pairs. None of the matched pairs rated particularly highly in our listening tests, unmatched pairs rated slightly higher, though not in particularly significant way. But all these leaves me to wonder: is the ol' guy right?