some old favourites:
SST RecorRAB - I was seriously OBSESSED with this label when I was 15/16
Touch & Go - another old favourite, loaRAB of good noise rock and post hardcore as well as some great early hardcore like Negative Approach and the Necros.
Gravity RecorRAB - focused more on emo, screamo and post hardcore banRAB, Antioch Arrow, Heroin, Mohinder, Clikatat Ikatowi, Angel Hair, Young Ginns and early Unwound were my favs on this one. A big favourite of mine when I was about 16.
and some more recently discovered favs:
Kranky - home to lots of excellent arabient, drone, early post-rock stuff. I think if you like one band on this label, chances are you'll enjoy the vast majority of the rest, like you said in your first post. Labradford, Stars of the Lid, Windy & Carl, Bowery Electric, GoRABpeed You Black Emperor's first EP, Low, Dead Texan, Jessica Bailiff, etc. All fantastic stuff.
Flying Nun - New Zealand label, and an incredibly consistent one. The Clean, The Verlaines and Bailter Space are my favourites but literally EVERY band I've heard who's on this label is well above average.
I put a lot of stock in labels actually, not really with music before the 80s though for whatever reason. There are millions of really great ones.