The therapeutic dose to hop up a person properly on a drug depends on the person really. Some people have to be doped up more than others.
25 mg of Seroquel knocks me out. I take it for anxiety and as a mood stabilizer.
Only a psychiatrist could give an exact answer but that's a subclinical dose generally used for a sleep aide. From what I remember when I was on Seroquel, 300 mg. was the lowest effective dose (and from what I was informed by my psychiatrist as well) and it didn't work if I lowered it any further.