Here's a link to the
Wiki contents pageWASAPI Event Style is more robust and generally a better choice if your hardware supports it.
Your hardware may be behaving more like pro audio gear so may require the option "Present 24-bit data in a 32-bit package" be set in the WASAPI output mode settings (Tools >> Options >> Audio).
You'll get more response to setup related questions in the Media Center 15 forum. The hardware related forums here don't get as many eyeballs. And there are people watching the Media Center 15 forum who are way more experienced in the various software configurations (and better at explaining it) than I am.
If you start a new thread in the MC15 forum be sure to include the link to the ComputerAudiophile that gives a brief listing of the specs for your gear. That way folks will know what you're dealing with and that it has lots of digital connection options. It will also let folks know that you've got something more similar to pro audio gear than regular consumer gear (pro audio USB DACs can behave a little differently than consumer USB DACs).
USB is probably going to be your best option. Though TOSLINK is also an option since I'm pretty sure your Mac has a TOSLINK output on it.
Getting streaming over WiFi to work well depends on the quality of your home WiFi network and how much interference there is around you. Does the Classe CP-800 have a connection for a wired ethernet connection instead of WiFi?