Hi Leafs,As you know I have the 99.My line stage has NOS G.E.6SN7"s my phono has Telefunkin 12AX7's and NOS Radiotechnique 12AU7's.I recently talked to Mark O.He told me he is getting in some KILLER NOS 6SN7's soon and is going to send me some.I know this doesnt help you out but I would get a hold of Mark as he gets feedback from Rogue owners on what tubes work best etc.He may even have some KILLER NOS tubes coming in for the 66 also.I dont know if you have ever had contact with him but he is a great guy and will be happy to talk to you or answer your questions via e-mail.I think he is the best bet to answer your questions on tubes for your 66..