Sonic Frontiers Line 1 Tube Upgrade

Hi guys, need some help in upgrading my Sonic Frontiers Line 1 tubes. There are 3 pairs of 6922, V1/LV1, V2/LV2 and V3/LV3. Which pair affect the sound most? Or should I change all 3 pairs? I am using RCA input and output. Also, which NOS tubes will you guys recommend?
Take a look here:
Hi Jeffcott,
Thanks for the link, I had read the disscusion before posting this question. I wrote to Sonic Frontiers and was told V2/LV2 affected the sound most and not V1/LV1 that I used to believe. So I am bit confused. Accordingly to Sonic Frontiers, function of 3 pairs of 6922 are as follows,
V1, LV1 - input buffer
V2, LV2 - gain stage
V3, LV3 - cathode follower