Sorry to post to an old thread, but today I finally got to hear a mainline with my utopia. I also heard a mogwai and a few other tube amps. I think the mainline held its own pretty well. While I sold my crack a long time ago, I’m building a new crack now. I know I said I liked the crack with utopia, but I was overly enthusiastic. The bass was a bit muddy with that combination. I did like the crack as pre to help get a little tube warmth, when needed.
With the mainline, the bass is very tight and impactful. I listed to a mogwai special edition, and it might have had a tighter bass, but it’s also considerably more expensive. Same with a number of Eddie Current amps.
I’m not sure I’m ready to take on another project just yet, but I’m pretty sure a mainline is in my future.