No thrash, yet you mentioned D666 as being a good band? I mean, if you like D666, you should like GOTH, Grenade, Denouncement Pyre, Razor of Occam, Atomizer, Nocturnal Graves and Destruktor.
Mournful Congregation - funeral doom
Long Voyage Back - melodic doom
Sadistik Exekution - epileptic black/death
Portal - avant garde death
Urgrund - black metal
Stargazer - avant garde death/black
Abyssic Hate - suicidal black
Rev. Kriss Hades - avant garde industrial black metal (guitarist of Nazul/SadEx)
Battalion - melodic black (similar to Dissection/Dawn)
Carbon - traditional black
Myrddraal - black metal
Spear of Longinus - black/thrash
Urgrund - black metal
Cauldron Black Ram - black/death
Misery's Omen - black/doom (think Bethlehem, but much better)
That's all I can think of for the moment.