Diwakarv,
FWIW, I have owned 3 CJ preamps (PV14L, ACT 2 and now GAT which is the same 'generation' as the ET3SE). The ACT 2 was not as susceptible to tube rolling, but I have found that going from the stock EH to Amperex 6922 to Mullard CV2493 (in my system, the Mullards MUST be used with EAT Tube dampers)...I found the preamp did adjust a meaningful amount. The voicing of the component did not change materially, but I did get a much lower noise floor with the 2 replacement tubes vs stock. I also found a much 'stronger signal' with greater fluidity with the Amperexes over the EH and much greater sense of linearity with the Mullards (which incidentally are the quietest of all...though that is probably tube-specific, as in literally the 2 specific tubes I got from the dealer).
I found the CJ GAT reacted favourably to isolation and damping on top (and by a considerably greater margin than tube rolling). Have not tried the ET3SE. Hope that is somewhat helpful since ET3SE is same tech/generation as GAT. Good luck.