Help with Cary CAD 120s II tubes

I have been trying different 6sn7 tubes in the 120, but have been switching all 4 out in matched sets. I do not know which slots are input, and which are drivers. Of the 4 positions which are most critical to change.

Also what power tubes work well in this amp? The amp currently has GL KT88 reissues.

Below from Cary's Billy Wright

"The front and back 6SN7 tubes are the input tubes. The ones left and right are the driver tubes. It is more important to make sure the input tubes are matched, and they also benefit more if you want to upgrade tubes such as NOS. I would still recommend matching the driver tubes as well."

Good Listening

When I had my Cary 120, I was able to purchase some Pope Holland 6SN7Gt tubes from Upscale Audio that really took that amp to another level.