I'm ready to ROLL!! (?)

[Feanor]

Tube aficionados, I hope you're with me now. My Sonic Frontiers Line 1 preamp arrived yesterday. I installed the six, standard, Sovtek 6922 tubes, and hooked it up. It's working just fine. This a sweet unit functionally: full-function; remote control; fully balanced outputs; and fairly handsome to look at, see below

How does it sound? Well, a wee bit better after a few minutes warm up. Other than that, this is super neutral preamp: it sounds very like my Adcom GFP-750 in passive mode -- nothing taken away, nothing added. Perhaps its a tiny bit purer on the highs, e.g. violins, and maybe even an even tinnier bit warmer in the upper bass. Great, but am I entirely satisfied??

Perhaps what I was really hoping for a bit more of that tauted tube warmth. But I'm not really getting it. Ok, maybe very slightly smoother highs but that's about it. What can I do? How about swapping, (i.e. "rolling" in quaint insider terminology), some tubes? The Line 1 has six 6922's: two input, two gain, two cathode follower (?). I've been advised that the gain, followed by the input, are the most important and most likely to be improved by rolling. On impuse I bought a match pair of new-old-stock Siemens E88CC tubes on eBay which have yet to arrive.

I want your suggestions. What's a course to a slightly warmer but no less resolved sound?
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