Ok I've tried all those settings. Couple of issues:
First of all, they're too quiet and make playing with headphones straight from the device impossible. So I plugged it to an audio interface so that I could increase volume and play with headphones from there (I'm using quality studio monitoring headphones btw).
Secondly, if you set amps with barely any gain, you're killing a great deal of their preamp character. So these settings make all amps sound very similar and uninteresting. Apart from a couple of exceptions, it's like they're all the same generic amp with slight EQ changes.
I'm pretty sure Line 6 did something wrong with these (I doubt you can't go above 2 or 3 gain out of 10 on a real life Ampeg SVT or Mesa 400 without getting lots of drive), but these settings aren't really a solution for me. I prefer to use the solid state models for now, which don't distort with cranked gain.