IMHO, I would really suggest that you just listen to the amp for at least a few months to let it break in and to get some idea of how it sounds, from bottom to top, and how it images. Also, how quiet it is. Find out how it sounds at low volumes and also at higher volumes. How much detail does it flesh out at low volumes, for instance? Then, AFTER you know what it sounds like, can you then make any judgements about tube swapping. Just my two cents worth, Happy Listening, and congratulations on your new amp. Sincerely,
