Originally Posted by mkk

From experience I'd say that a higher number of bits can make a definite improvement even with sounds played back from 16bit sources. But I don't know what good a higher frequency would do as there is probably no active sampe rate conversion going on. Until you get a better answer than that you could simply try the highest setting out and listen if it sounds alright. If set too high for the card/driver the sound might start to crackle or distort.