Along with this problem I have a number of other bugs/glitches that I've been unable to resolve so I think at this point it's time to just chalk it up to Media Center for Mac is a "work in progress" and hope that a future upgrade fixes some of them.
I don't think you're right about that. The Mac version and the Windows version are very, very close. The Mac version is updated regularly with all of the changes that the Windows version gets too. There are a few Windows features not in the Mac version, but not very many.
This particular problem you have is with network audio (DLNA/UPNP). There are threads in this forum about various problems like this ALL THE TIME with MC for Windows. That's why I originally tried to gently suggest that you'd be better off connecting your DAC directly to your Mac via USB or optical digital. These kinds of problems don't generally happen with a direct connected DAC.
You may still be able to find some way to make MC work with your Logitech network audio server. I only read these threads; I don't have much expertise in this particular area. A different server might work more fully with MC if it is more DLNA compliant. The vast majority of USB and optical DACs will plug in to the Mac and "just work" with little extra configuration.
You mention other issues you are having. I don't remember reading about them, but maybe I missed or forgot them. Start new threads, or update existing ones and we'll try to help you with those. Unless these other issues are all related to sending audio to your Logitech? In which case they (probably) are all due to the same DLNA incompatibility.
Brian.