Having just entered the fray again with amplifiers that use very fragile tubes I have noted that the best prices are available only at the origin of the tubes. A Winged C 6AS7 here is $45.00 but from Russia is $15.00. Shipping for 40 tubes was 20 dollars! Check out TubeTerra. The same holds true for 6NS7s but the very best NOS tubes are only available from Russia for a whopping $8.00 per tube. I had to do a lot of research to find these tubes. You do not have to be gouged by American vendors. Get your tubes where they get them from.