regarding tubes replacement with NOS tubes, do we have to change all four of them or just the front or back set? also I notice the faceplate of the demo unit at the dealer is different from the picture I see in many forums, including audio valve website, the characters of the words "eklipse" is different, and also the characters on the input is different, other than that looks pretty much the same. I asked if the unit was made in germany and he said yes. is it the newest version?