Playing back lossless 5.1 files over a network

[twigsta]

Hi! n00b here, be gentle.

I own a Yamaha RX-677 receiver set up in 5.1 configuration.

I'm trying to play back lossless surround version of Pink Floyd's Dark side of the Moon that has been backed up from a DVD-Audio disc to DTS 5.1 FLACS and WAVS that are hosted on a Plex Media Server.

I've checked the files using VLC and they play back fine on my Mac.

The specs say the receiver is capable of playing these files as flacs, wavs or DSD files, and I was hoping to be able to sell my old DVD player and free up some space and transfer my surround Audio to the home server.

I've tried playing it with the RX-677 amp client, and I just get static.
I've tried playing it with both the Plex app and the default DLNA client on my Samsung TV but it doesn't recognise the codecs.
I've tried playing it on an Apple TV, apparently the ATV is capable of decoding WAVs encoded in DTS 5.1, but I just get static.
I've tried playing it with the Plex client on a Roku 3, and I just get the Left and right channels (although Netflix does play 5.1 so I know that's working) - it's the closest I've got.

Has anybody successfully played these files over a network? Does anyone have any suggestions about where to go next?

Thanks in advace,

[blacksheep]

What codecs, Mac and OS are you using?