To be fair, TAD at least provides some data with theirs. Buying a matched pair from [XYZ] and getting two or four valves that are nowhere close is a raw deal. Honestly, good valves, bad valves - balance makes a big(ger) difference in the output stage in my opinion. That's what TAD provides, though I'd rather buy something knowing what brand it really is. Any competent seller can check and match valves before selling them - it's not rocket science.