Johsti,
I have digital volume controls on my CD players and I can't hear any difference is SQ at low volume settings either. But if you are worried about over driving a preamp, you may have some global gain settings somewhere on your DAC or CD player. Mine do, but to access them I have to open them up and set some dip switches they give you. Its a very useful feature but quite often people that have these players don't know about it.
I have digital volume controls on my CD players and I can't hear any difference is SQ at low volume settings either. But if you are worried about over driving a preamp, you may have some global gain settings somewhere on your DAC or CD player. Mine do, but to access them I have to open them up and set some dip switches they give you. Its a very useful feature but quite often people that have these players don't know about it.