I don't have any of the weblinks to graphics and explanations available atm, but if you dig around on the forum communities that go into a lot of technical detail on high-end sources (not HF or AGon), as well as look at some of the manufacturer websites (particularly ones with engineers possessing strong hardware and software backgrounds), you'll find various measurements, graphs, and the occasional white paper. Digital audio is a much more difficult problem than most people recognize, as it conceptually seems like such an easy thing to turn a media file into a waveform, but it's actually a very difficult and multidisciplinary field.
The easiest test is to just use your ears, such as seeing if you can pick up on differences while your computer doesn't have a lot of available resources and are running multiple active threads at once. A lot of people obsess too much over not having the absolute best sound reproduction possible. If you don't hear a difference, then it's not worth fussing about.
A lot of people have varying opinions on the sound signature of DS vs WASAPI (and many more don't hear any difference at all). My own personal experience is that WASAPI sounds more neutral and transparent, which I pick up in vocals, bass, fast low frequency passages, and cymbals. Consequently, WASAPI sounds a little more clear and resonant, depending upon the recording environment. Ever since I got my WaveLink HS, it's gotten easier picking up on the nuances of the recording environment for certain recordings (like hearing a slight echo after voices hit the walls in a room), as well as little things like fingertips lightly pressing on violin or cello strings, or the vocalist breathing lightly in the middle of a song. I didn't get this detail retrieval until I drastically improved my signal chain, and WASAPI vs. DS didn't really have an impact until my setup went through a lot of adjustments. Some of it may be placebo on my side, but A/B testing Foobar vs JPlay is pretty surprising. JPlay easily accentuates details which I sometimes only pick up on Foobar if I'm (a) listening very loudly or (b) doing critical listening.
Again, mileage varies drastically depending upon the quality of the recording.
I continue to use a properly configured Foobar as my control, as it's the most neutral of the nearly two dozen audio software (Mac and PC) I've used in the last year. If I have music playing as background noise at work, WMP/iTunes is fine, but if I'm on my electrostat setup, WMP/iTunes has a bothersome haze and veil to the music. It's not prominent, but enough of it is there to irritate, kind of like a paper cut once you realize it's there.
