Okay. While HDMI can be run quite long distances, that sounds like a pain.
Can you confirm you are only going to use MC to play music, and will never use it to play video or TV? That makes a big difference.
If you are only going to use it for audio, then you can definitely use DLNA to send the sound from MC to a Receiver. So no, you will not be forced to listen to things through iTunes! (I assume, given the location of the PC, that you would have been doing that in front of the PC with headphones or something? After all, iTunes runs on a PC and if that is where it is running then you still can't get the sound to your Thiel speakers.)
As Jmone mentioned with his AVR, many AVR's only support DLNA for audio, and many only support stereo audio. DLNA compliant doesn't mean it supports all DLNA specifications or capabilities. Even though the Yamaha RX-V773WA Receiver says it has "4K Upscaling for next generation super high resolution displays, and HDMI (4 in/1 out) with 3D" that doesn't mean it is a DLNA video renderer, which you would need if you wanted to push video from MC to the AVR via DLNA. As far as I can tell from the Yamaha RX-V773WA Receiver manual, it is a DLNA Audio Renderer only. If audio is all you need, fine, but think about what you may want to use the AVR for in future as well.
Note that in the manual under DLNA Playback, page 65, it says of the Yamaha RX-V773WA Receiver, "The unit is compatible with sampling rates of up to 96 kHz for WAV and FLAC files, and 48 kHz for other files." That would exclude this unit from selection for me if I had to use DLNA for audio playback. After all, if I am going to use FLAC files I want to be able to play 24 bit / 192 kHz music.
Note also that this receiver is restricted to 24 bit / 96 kHz when played in 8 channel mode, but supports 24 bit / 192 kHz in 6 channel mode. Probably not an issue, since most 24 bit / 192 kHz audio is 2 channel anyway, and the receiver supports Dolby TrueHD and DTS MAster Audio, both of which have the same restriction.