If you use standard Doom 3, be sure that /image_downSize is at 0
It was stuck at 1 for me (blurry textures) despite trying several times the ultra setting and restarting the game.
When i tried auto settings the game was not detecting my GFX card memory (according to the msg in console). The problem was maybe here.
Or simply use dhewm3, everything should be fine without tweaking and you will get OpenAL sound (reverb effects, etc).