audio valve eklipse or aesthetix calypso

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?

Kabaraka, Audio Valve will tell you that the pair of tubes on the left, assuming your looking at the preamp from the front, are the lead tubes and therefore are more important then the other pair of tubes. My experience has been that both set of tubes are important to get the highest level of performance out of the Eklipse. So yes, change all four tubes when you tube roll. Can't answer your question regarding the spelling on the front plate, unless your dealer has an older model.

thanks again Teajay,I'll try tube rolling after getting the unit. I notice a little roll off on the high frequencies or may be it's the warm characteristic of the eklipse.may be the dealer set up.

Update.
I revisited tube rolling with my Eclipse.
A pair of NOS 5960 really did smooth things out and take a harsh edge off of what I had previously felt was decent sound.
I agree completely that better tubes (left side)make this an even better pre amp.
The RCA clear tops that I had tried (bought used)must have been sub standard or used up.

Update! just got the eklipse yesterday and the dealer also offered a demo unit which is very new of the Coda CSX amp so I took it home too. The eklipse is being ran in and it sounds fabulous already. Thanks all for the comments. Anyway,any opinion on this Coda amp is welcomed.
Cheers