I hope you don't mind a friend and dealer of Modwright pitching in?
I'm a big fan of this pre ( and all Dan's work), first of all, I've noticed that this unit responds dramatically to different tubes and any reviews based on stock tubes can be discounted, with the Sophia's it is a very detailed, musical and actually pretty neutral pre.
the 'warmth' to me is not the "covering the tone with tubes" warmth but instead comes from a more complete passing through of the source. more extension, detail, nuance etc.
btw I also use JC2 as one my solid state reference pre and agree that I prefer to listen to the LS100, I just find there is more music there. not that I mind the JC2 
thanks,
lou
Agreed once again. I may not be the most experienced at describing or reviewing audio equipment. I think when I write about 'warmth', 'liquidity', or even 'richness' to the sound, this might be the same thing that some people just call 'musical' or 'natural'.
However, I definitely think that what I like best about the LS100 has to do with tone, more than anything else. Another word being used a lot here is 'nuance', and that would be another thing to keep in mind when thinking about the sound of the LS100. While some ultra-detailed equipment may sometimes have a tendency to sound sterile or bright (and fatiguing), the LS100 most certainly does not! It seems to have the same level of detail while allowing these nuances to meld in and make for a very natural and musical experience.
Whether this end result is something that is 'injected' into the sound by the LS100, or if the LS100 is simply allowing what was there in the signal all along to come through so beautifully is not that important to me, personally. I have tended to think that the LS100 adds something to the sound, only because the nuances of this added tone can be altered ever so slightly by changing out various tubes. But perhaps my logic is flawed. I only know that I love the way it sounds.
For what it's worth, I am currently using a pair of 50's era Sylvania chrome top 6SN7 tubes. In the future, I plan to try out some of the new production Sophia Electric or Shuguang Black Treasure tubes that are so often talked about. I loved the sound from the LS100 so much that I gave up my other solid state amp with about twice the power handling, and got a matching Modwright KWA100SE amp for what i feel is better overall symbiosis.