When you say 70dB where are you taking that measurement?
At the (speaker) source, X feet away from the source?
At your listening position, if so are you seated or standing and how far above / below your ears are the speaker drivers?
Also, since you specified classical music - is 70db an 'average' reading throughout a piece, or a crescendo or lull reading..?
For myself, I generally find listening at around 80dB to be the 'sweet spot' in my particular listening environment (18 X 40 ft room, approx. 12 feet from the speakers, most musical genres) and this equates to about 1 watt per channel of output from my system.
I have noted that, specifically when listening to classical music, I find it more sonically pleasing to lower the volume slightly - as I feel like the changes between soft passages and louder parts seem more abrupt and less subtle to my ears, than for example jazz or even moderate rock music...