I like this. I've had my gain in the 2-4 for a while, and adjust the master for volume. I like the feel of the amp (the way it responds to touch) better with the gain low.
I've tried the Gain high method at home and on a few gigs. It's OK. When I get to about 5 or 6 the amp seem to stiffen up. Usable but you loose some touch feel IMO. Good tone for a more straight forward rock oriented sound. One I get to about 8 on the gain, it starts to "break up", but (IMO) it's not really a usable or natural sounding beak up. In fact, I'd say it's more of a clipping than break up sound.
I don't really get a tube amp vibe from the quilter. Maybe a big supper clean tube amp like a Hiwatt DR201 or something. I get more of big-ole SS vibe - reminds me of my old Thunderfunk 800. I think of the BB800 as part of that whole Acoustic, AMP, Thunderfunk family tree.