Hi Mike!
Your juices are flowing....your interest is peaked! That's a good thing because you have one of those systems that's ripe for DSD 128! Resolution wont be a problem for your rig. And DSD 128 done right is jaw dropping enjoyable!
Jriver is great, especially when you add JPlay which isnt so easy any more from what I gather, due to the feud between Jriver and Jplay.. But Fidelizer Optimizer is good as well and there's a free version.....here's the link.
http://www.fidelizer-audio.com/
Don't forget to read the support page on Jriver...lots of info in there on getting started.
Acoustic sounds has some downloads that are DSD. And you may know about HD Tracks as well. A few others.
http://bluecoastrecords.com/ http://www.channelclassics.com/ http://www.cybele.de/ http://www.hifitrack.com/en
If W4S DAC can do native DSD, then you pick the ASIO option in Jriver and it sends DSD to the DAC, if not, then you'd select the WASAPI option which sends DSD in a PCM wraper until the DAC lets you in, then unpacks it as DSD. Once you get use to it, it will be second nature.
Once you start reading about DSD, you'll find stuff out there...lots of white paper which talks about noise with DSD and that Hi REZ PCM is the way to go. I have not found that to be true....at least not with the iFI Products in my experience. But once you find your way around DSD and PCM let your ears be the judge, not whats being reported in reviews. I was at a DAC party a few weeks ago where there was a $10k Bricasti DAC....a $8K DAC Which was that high dollar Cary Audio Music system DAC, and a $3500 Marantz DAC as well as a $1500 Cambridge DAC. The first 3 all had DSD capability's. Because the guy who gave the party read what some of those reports said in the negative about DSD, he wouldn't even up sample and do DSD on the fly. So kindly let your ears tell you whats up.
Let me know how you're getting on with it...and if you need help, feel free to ask.