I only bought one Gold Lion ECC83/B759 in part due to the high cost, and the other wanted to find out what all the hype was all about. Even though it looks like an identical tube to the Sovtek LPS or Mullard 12ax7, it did sound slightly different when it was not making the pop corn sound. I even tried a Northern Electric 12ax7 which is similar in construction to the NOS RFT 12AT7 I have in use in my RA100. That actually sounded nice but it too suffered the ping noise when changing channels due to the shift in operating point of the triode circuit. A NOS JAN/GE 5157 did make a difference in V1 or V2 (with a stock tube in V1) which was quite interesting. The slight reduction in gain as well as the overall brightness of the 5157 (also slight drop in mids) seemed to give the Roadster a vintage vibe to it. The Roadster is a bit different than the other Rectifiers as the cathode follower circuits use different tube positions (more than likely due to the reverb circuit). To be honest, I have used Tung Sol and stock Mesa tubes more than the others. Currently, I have all mesa 12ax7 in all of my amps, and the Roadster is the only one with Stock Power tubes. Both the Mark V and Roadster I am using a Mesa SPAX7 in V1. I may end up installing a stock tube in V1 of the Roadster just to hear the difference since it has been so long since I have used the standard tube there.
Both the JJ sourced tubes (current Mesa 12ax7) and the Shuguang 12ax7A will hold up in a cathode follower where as the soviet tubes (mallard, tung sol, eH, Gold lion, Svetlana, Sovtek, etc...) will not. Check your amp manual for tube position assignments ("tone stack", and "FX Send" circuits are cathode followers.) I believe you can find a list of models and what tube positions are what for the majority of Mesa amps in the Rectifier forums, it is one of the sticky notes at the top.
Change in the tone stack tube (should also have another gain stage associated with it) will not do much for changing tone of the amp. A lower gain tube may also increase the low frequency response of the amp (increase, not decrease). What I found thus far for V1 in my Roadster was the Mesa SPAX7. Many use a Tung Sol in V1 which does seem to reduce the bottom end and enhance the higher frequencies. The case with the Roadster and CH4, it is much darker in character than the other channels. How the response will be in your amp is unknown. The low end and top end of the amp is already designed into the gain stages, tubes will enhance or subdue some of the characteristics but will not remove them entirely. Tube rolling can be interesting in one respect but can also be disappointing in others. One other tube position that is often overlooked is the PI tube. This may not effect the gain character of the amp but will affect tone structure. In the Roadster, the Sovtek LPS did brighten up the amp almost as much as a Tung Sol in V1. However, I have become addicted to the character of the Mesa 6L6GC with the stock tubes in all positions as the grinding sound from moderate distortion is more 3D sounding. I would poll your question in the Rectifier forums for opinions about effects of the change in V1 tube relating to your amp.