Tenhi and Nest are both fucking excellent bands, but neither are dark ambient. they're neo-folk...as acknowledged in the previous post *cough* (though Nest may be considered something else)
some excellent dark ambient projects:
Nurse With Wound
Gruntsplatter
Lustmord
Nothing
Irr.App.Ext
COIL
Bohren Und Der Club of Gore (not really "dark ambient", but good enough)
Atrium Carceri
Elend
Robert Rich
Blood Box
Northaunt
that should keep you busy for a while