Thanks to all for your thoughtful responses. I have had experience with all of the stock Line series pre-amps, and I also own a Line 1 that I use in a "sort of" HT set-up. But I've also used the Line 1 in my stereo system, and Jason is right in that there is not a big difference in music quality between the Line 2 and Line 1-- still, I prefer the Line 2 for music-- it's a bit smoother and more refined.
Mario; 2-3 years ago I did audition a Line 3 in my system for about a week and it produced that "big bloomy diffuse forward" sound effect that I dislike so much. I now have somewhat different components and wires, and I'd like to try it again, but it's difficult to arrange as I live out in the boondocks. Your involvement in the SE up-grades is interesting.
Re the SF website, the up-grade for the Line 2 is $999. USD, or $585. without the Seimens/Brimar tubes.
As of now, I'm leaning toward having the upgrade done and getting the new tube set too-- then if I don't like the new tubes, I'd hope I could exchange them for the stock Sovteks with SF. I've done some tube rolling with the Line 2, and keep going back to the very neutral stock Sovteks.
I may start another thread about what causes that "big bloomy diffuse" sound character that I don't like at all-- it sounds very un-natural to me. Any comments on this? I don't know what causes it, but I've had it happen with a Levinson 331 amp, SF Line 3 pre-amp, an ESP power cord, and two different set of NOS tubes in my Line 2. I have assumed there is some kind of weird electical reaction going on that produces it in my system.
From the above responses, it looks like everyone thinks the SE upgrade is worthwhile for any of the Line series pre-amps. David, thanks for the encouragement. In this hobby, we've always got to have the "next and final?" up-grade in the planning stage at least ;>). Thanks, and Cheers. Craig