The up2stream pro v3 is a pre-amp board. It is not an amplifier board. You can put this in between the tv and the KABD-4100. You can buy the additional S/PDIF in or out, along with a DAC if you want.
You are right to worry about the conversions, as each component may have a certain noise level. Now, you can noise gate with the KABD so that any noise below that point is chopped off the signal before amplification. Can’t fix the noise from the amplifier itself, though. So keep that in mind.
For example, the first one is an HDMI passthrough with audio extractor for a stereo out using RCA. Just put this in between your set top box or cable box and the tv, then feed the audio into the arylic I linked using RCA to headphone jack, then use the headphone to headphone to link to the KABD-4100, then out to the speakers.
For the second one I listed, it has 5 HDMI in, 1 HDMI out, and headphone stereo out. Just do headphone terminal straight line to the Arylic, then same cord to feed to the KABD-4100, then to the speakers. Done.
Now, if you need 4K@60Hz and HDCP 2.2 support, here is a product that claims that.
And when I say headphone, I mean 3.5mm Aux stereo out. But you get it. Make sure whichever audio extractor you use, you check the features, such as resolution and refresh rate, output terminals, HDCP support (more important than you think, and the avedio are some of the few listing that support; if you don’t get an HDCP handshake, some video will not playback).
Further, if you do go with the Arylic for a setup like this, I’d use the accessory DAC as the KABD-4100 doesn’t have a digital in. That port is used to link together two KABD-4100s to build an 8 channel audio situation. So you would have to have a DAC to switch the digital internet content over into analog to send out the 3.5mm Aux port.
On the expansion boards, I’d grab the DAC and the IR extender, then pickup the remote.
What you are basically doing is building a pre-amp receiver. You have the HDMI audio extractor feeding into the Arylic as a pre-amp, which can also stream audio from your internet digital services, which then converts the digital to analog for output or does passthrough output to the KABD-4100 DSP and Amplifier combo. You then can use that remote to adjust the volume of the entire chain from across the room.
So, you are building your system around your required specs, rather than buying a receiver that does it, but might only have some of the features you want and many you don’t which increase the price to buy a receiver.
Hope this gives you more information.