From what I can gather there is very little difference in sound quality between Directsound, WASAPI and ASIO since Windows Vista, which introduced a 32bit floating point sample depth to the audio stack.
an interesting read on the subject...
http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/
an interesting read on the subject...
http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/
