Listening to Bayers 1770 pro with the Quickstep off sr25mkii using ADL by Furutech iD 35R "hipster
" interconnect cable.
Quickstep drives these 250ohm Bayers absolutely fine I am happy with it (I am considering 2nd backup pair because the more I listen to this amp the more I like it because it softens these Bayer highs a bit).
I like the clarity/detail/air also punch in midbass and its ability to drive my Bayers more than I would need or want.
Sound wise difference between battery powered vs 15v adapter powered quickstep is about the same do not expect miracles (10 percent improvement off the 15v adapter I would say nothing that would convince me to use the adapter instead) I prefer the battery powered because convenience.