I haven't listened to any of those bands beside Ars Diavoli (which are awesome), but I do listen to some of the more ambient/DSBM-type black metal.
You definitely want to check out:
Velvet Cacoon - p aa opal poere Pr. 33 (very ambient, very drone)
Menace Ruine -
In Vulva Infernum (not very depressive, but very much droning/ambient, great stuff)
Sui Caedere -
Threne (more depressive, a bit folky, no droning tendencies)
Gris -
Il Etait Une Foret
Heretoir -
Wiedersehen
Unsere hoffnung (depressive with a blackgaze kinda vibe, awesome split with Thränenkind)
Thränenkind -
De euphorie des augenblicks (very "clean sounding" depressive, lots of Amesoeurs-influences)
Austere -
To Lay Like Old Ashes (really fricking bleak, while still being somewhat melodic)
Nyktalgia -
Nyktalgia (very up-tempo depressive bm)
Also, in case you missed the obvious: Burzum's
Filosofem and
Hvis Lyset Tar Oss are essential. Not strictly speaking DSBM, but the scene probably wouldn't exist today if it weren't for those albums.