Re: CD, SACD & DVD-A
Have you considered connecting your PC to your receiver through its audio out ports, or possibly using an AppleTV or other such bridge and so using the PC as the playback device? I have connected my PC (through a VCR's audio inputs, interestingly enough) and from the VCR to the video's sound-in port of my A/V receiver. Video devices, as you probably know, have very high bandwidth capacity and audio through them might be as good as one of these super-high resolution FLAC files.
For this to work, you'd still need one thing: the software on the computer that can play back high-bitrate encoded music files. But if you used your PC for storage and decoding and your sound card for digital-analog conversion and output, I don't see why you could not get these files to play through your receiver.
"I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone."
— Bjarne Stroustrup (creator of C++)