Have you tried the Jan-Philips ? Those are glass 6SJ7, others from RCA, Tung-Sol etc are metal tubes which may have a different signature.
Concering this new switch, would someone enlighten me how would it reduce the hum ? My wide guess, it does not reduce the hum of the tubes as such but changes the impedence interface with the headphones such that the hum was more faded into the background for the same volume. Would dynamics and other aspects not change too in the process ? My RSA P-51 Mustang has a high / med / low switch and they do not sound the same to me. This is not to say that it is becoming a Meier with different setting, but you don't just change the output level, many things get affected too. It is not a case of have your cake and eat it too, but still probably much better than spoiled by the hums. I guess the best thing is still to search for a set of quiet tubes.
Now if you are willing to trade-in your quiet tubes for my vintage matched pair of Tung-Sol....