Picking an amplifier

Motherboard: Asus Z170-A (LGA1151) motherboard has optical link by RealTek->Sony DSP-EP9ES 
Windows 10
Browsers: Chrome, IE 
Videos are on VLC media player unless it's a bizarre format, then I either find a codec or dig up something that handles it native. 
Realtek & VLC player have various EQ & audio modifiers (ambiance, compression, room correction, DTS Studiosound, DTS settings)  Most of the time I find that the audio hardware & Sony settings suits my taste w/o modification. 
Optical outs on MOBOs are almost a unicorn. Right now I see 10 on Newegg (out of hundreds)
I'm looking around for a site that reviews the various DAC chips. A site that contains a list of who's using what classes of amps by model. We have such a thing for various computer components. Hard disk drives, motherboards, etc. 

@shalmaneser – Thanks for responding with all that detail!  If you want to stay with using your computer, that’s totally find.  I can respect that.  Though, I will say that I have been there with you.  Many years ago, I used to run an HTPC for all my audio/video processing, with custom modified video cards using BNC RBGHV outputs and specialized sound cards.  I have then moved on to dedicated components, which just worked so much better.

That being said, I have experience with what you are doing.  I will say that the optical outputs on these motherboards are really poor.  The reason is lack of good digital clock and lack of good local power supply filtering.  Also, the optical interface is lacking when compared to digital coax.  I would highly recommend getting a good sound card with spdif output.  Since you are running Windows 10, the only one I can see that supports Windows 10 drivers is the Xonar Essence ST / STX / STX II.  Any one of these will work.  They all have two crystal clocks that are based on the two primary audio sampling rates (which are 44.1/88.2/176.4 or 48/96/192).  I think I read the older ST PCI card had better digital clock section but they would require an open “PCI” slot.  The STX models are the newer PCIE cards.  These are going on ebay for $50-90.  Then get that 6 foot Blue Jean Beldon COAX cable.  I’ve tested the motherboard optical outputs and they just sound weak in comparison.  The idea that “it’s just data until it hits the DAC” is not an accurate statement here.  The VLC player should have a configuration that allows you to send “spdif passthrough” on the digital spdif output of the sound card (even for AC3 and DTS movie bitstreams).

At this point, I think you will need to decide if you are wanting to keep your Sony processor and get an amplifier, or look for a really high-end receiver.  Just keep in mind that Sony is definitely a limiting factor because it won’t even do DTS (which is the format that is most used nowadays).  The Bluray DTS-MA HD will be automatically downconverted to normal oldschool DTS before it is sent out on the spdif digital output.  The only digital connection that supports hi-res bluray is HDMI.  You could get a video card with HDMI output and run it through a new receiver with HDMI inputs if you wanted to truly decode hi-res bluray audio.  Though, it may not sound better unless the receiver was up to par.

A oppo 103 with denon 5803 via multi-ch input will give you DTS-MA HD
Or Using the OPPO as a pre-amplifier direct to power amp

Fun and games understanding audio:
http://h-cat.com/images/H_CAT_White_Paper.pdf

And the winner is: 
https://www.audiostream.com/content/holo-spring-dac-level-1

" Holy crap! I'd plugged in nine devices just to get my file to the DAC. But I had to admit that the sound and musical connection this Rube Goldberg playback chain provided was immensely better than what was possible with a laptop or even most dedicated servers connected directly to the DAC."

I'm losing count of the papers written on the dubious digital improvements over vinyl->amplifier->speakers. It gets worse: most of the DACs don't improve on the original DAC technology. The improvements come from a host of analogue pre/post DAC fiddling at great expense. 

auxinput: I've resolved one problem I've been having - every once in a while windows OS & software demonstrates its dubious roots of lack of 7x24 orientation and things need rebooting. (Microsoft: 3rd rate software company with top shelf marketing and lawyers) It happens less and less frequently and sometimes it appears to be hardware related. If civilization was created the same way which software is, the first woodpecker to come along would be the end of civilization. The other amp just needs someone to go through it and find whatever's going on. 
Thanks for the update on the digital world. Eventually MOBOs will fold a decent DAC into the consumer level. Until then, Rube Goldberg lives! I think I've got a PCI card slot free. If not, I'm building another computer soon and will configure it appropriately for the AV room. 
I'm waiting on upgrading the Sony till I can drop another $1K on a component. So far the Anthem 5/50 amps are very appealing. The professional reviews and consumer comments have negligible negatives and it's amazing how excited people get when they are writing about them. Or someone worked very hard to organize a positive campaign.