Well, in general it have two outputs , one balanced and the other one unbalanced, i generally the balanced one soundstage is bigger with more seperation, more depth, more layering to the sound, the unbalanced sound more narrow and less open, maybe the the balanced one is more pristine, i have also g111 lake people and the unbalanced sound better.
I checked the fostex th808, th909 on the lowest gain and its not good for them, also the g111 not good for them (they are very hard to drive in a good way). If you use planar headphones this amp will be good , if no then skip on this version