Thanks Jax2, Newbee, Detlof... Impressive amount of information on tubes! Tubes were totally unknown for me. But I have learned a lot for the last two days (I think I have, that is...). 1. NOS are USUALLY better than current production tubes; 2. NOS are many times fake BUT there are some dealers we can trust (like Jon) 3. Power tubes need to be matched. Preamp tubes also but it seems to be not as important as for power tubes. The same for NOS 4. There is no such thing (as there isn't for all audio matters) like the best tube. It will depend on the system and, of course, on personal taste. Nevertheless, within the ECC82 family, models like Amperex 7316, Tesla ECC802S, Sylvania GB-5814A or Siemens ECC82 seem to be worth a listen. So, I have one more question: according to your personal taste, and considering the tubes listed above or other, which ones do you like the best? And still one other remark: I do apologise for my English... Thanks!