To be prepared for my next upgrade, I have been searching for a 4K HDMI solution. Besides HDMI 2.0 and HDCP 2.2, bit streaming of all HD audio formats like DTS-HD Master, Dolby TrueHD, and Dolby Atmos are on my wish list. Though MC might do a good job decoding HD formats to PCM, I still prefer using the features of my AVR, where I can configure audio options from remote. Even more, the immersive formats Atmos, Auro-3D, and DTS:X require bit streaming to decode my current 5.1.4 configuration. What else is on my whish list is DoP over HDMI.
I had some disappointing attempts with an i7-6700 IGP graphics on an ASRock Z170 Gaming-iTX/ac board equipped with an MCDP2800 converting DP 1.2a to HDMI 2.0, and an NVidia Zotac GTX 960 AMP 4GB based on the 4K GM206 chip. With those the HDMI signal was not very stable when turning off/on the AVR or TV. And even more, regardless what I tried to configure, HD bit streaming was not possible.
Since some weeks I now have a Gigabyte Radeon RX 460 WindForce OC 4GB in use. Due to the compact height without protruding power connectors on top, the card fits well into my OrigenAE S14V case. And with its zero-fan-mode the card remains quiet during playback. An advantage of the RX460 over the RX470/80 is, that it completely powers down each idle GPU kernel. So, in idle mode a combination of an RX460 with a C236 mainboard will consume less than 10 watts.
The HTPC is connected via an X-7200WA AVR to my VTW60 plasma. Picture and sound remain stable when turning off/on the AVR, and even with the TV off the sound continues. All HD sound formats are properly forwarded, including DTS-HD Master and Dolby Atmos. And even 10-bit color resolution works well.
If one day DSD (SACD Audio) pass-through might become possible, it would be the perfect HTPC card.
Regarding the mainboard, I want to replace the ASRock iTX with a Fujitsu D3417-B (cheaper) or Supermicro X11SAE-M (more features). Both are µATX-sized without any protruding SATA connectors, as only such fit into the S14V case.