I am currently using a line 3 in my system. If you don't like the line 2 then you probably won't like the line 3. Perhaps you should try changing the tubes in the line 2. I would recommend calling Sonic Frontiers. When I talked to them last, they mentioned that they stock other tubes besides the Sovteks. These other tubes supposedly don't sound as neutral as the Sovteks. I like the stock neutral sound so I did not try this.
Want to upgrade my Sonic Frontiers Line2
What should I look at to improve on the SFL2? Under $5k used