Tube Rolling in a SF Line 3

Changing the 6HG8A pair will have little effect. The biggest sonical improvement can be made by swapping the last pair of 6922's (at the rear of your amp).
This was a suggestion of Kevin Deal from Upscale Audio; the guy is an expert on tubes and Sonic Frontiers.
Try matched NOS Amperex 7308 in these positions, keep the Sovtek's in the other and you will hear another amp at moderate costs.

Agreed. If you want to further experiment, stick to that pair of 6922s.

Agree with Peterb, just those two tubes made a big sonic improvement.

Many thanks. Just what I needed to know.

Changing the 6HG8A pair will have no effect. As mentioned only the back two (2) tubes are affected by the sound of the SF Line 3. I have found the Amperex 7308 JAN's or USN to sound superior, of course this is debateable. I have found the Amperex 7308 PQ's less desirable. Changing those back two (2) tubes was worth the effort, with the Sovtek's hand I found the nearset lake and made ripples in the water, may they rest forever in peace. Good luck!

After changing the significant pair of tubes, you can add a tunable tweak: try a pair of Shun Mook tube resonators.
By rotating these ebony caps you can choose for extra warmth or focus. Great stuff !

Amperex green label 7308s in the rear outside pair elevates the Line 3's performance considerably. This particular tube fleshes out the rather lean character of the stock tubes and eliminates some glare/brightness in the upper mids/lower treble. Dynamics and resolution are also enhanced. I bought mine from Upscale Audio's 'cookie jar', available only to those who have purchased their units from Kevin. I've also tried NOS Jan Phillips 6HG8As. These added a nice warm tonal balance, however these tubes also collapsed the large, airy and detailed soundstage provided by the stock Jan Phillips 6U8As. I've just retubed my Line 3 and currently have a MP Jan Phillips 6U8As, MP Amperex 7308 green labels in the rear outside positions, and 4 MP 70s vintage Sovtek 6922s. The latter are only slightly better then current production Sovtek 6922. A bit smoother, and a little more robust in the lower octaves. So if budget is a consideration current production Sovteks would work fine.