Thanks Miles, I appreciate your reply. One of my main concerns is the bias setting. As you know, Mesa amps do not have a bias adjustment. This can be good or bad depending on your outlook. On one hand, I won't be screwing up any bias settings because there aren't any ajustments to make and if I purchase spec tubes right from Mesa, then I have nothing to worry about. On the other hand if I buy Svetlana for example, I may or may not have a problem. There is no way to tell until they are purchased and installed. I guess from my point of view and my geographical location, I'll just made the best decision I can based on my reading and see how they work once installed. Thanks again for your help.