Need help with setting up a networked audio system

[Fureniku]

Hi guys!

So I'll jump straight to the point. I've got a number of audio inputs, and a number of outputs, and I want them to all play nicely together - so I'm looking for my best option on how to achieve this.

I have:
NOISY THINGS
- My TV (with a few games consoles, Chromecast, and TV itself). It has an optical audio out (No 3.5mm, not even a headphone jack)
- My computer, which has both optical and 3.5mm out
- My guitar amp, which has stereo 1/4", stereo XLR, or coaxial optical out
- an Alexa echo dot, which has 3.5mm out
- a Raspberry Pi, which has 3.5mm out (this one is less important).

I want all of these to be able to simultaneously send sound to...
SPEAKERS
- Main PC speakers, by my PC. Optical or 3.5mm input
- Rokit KRK monitors, by the TV and my keyboard (which is played through PC). 1/4" or XLR input, one on each speaker
- My PC headset, which is connected wirelessly via a proprietary dongle. (This is pretty much my problem causer, but I really like the headset and dont want to replace it if at all possible)

The key here is that I need to send sound sources simultaneously, not switch between them. There are cases where I would want multiple sound sources coming through at the same time. Depending on things like time of day, I might want my TV to come through my headset, or my guitar to come through the monitors, so I need to be able to move things around relatively easily too. Finally, latency is a big deal, I need as low latency as possible for both the instruments and playing games on PC or TV. One other important note is that other devices still need to work when the PC is off - Especially the Echo Dot and TV, as both of these will be in use frequently when PC is off.

I also have two audio interfaces, both Focusrite:
- Scarlett 18i6 (coax optical 1in 1out, 2x xlr in, 6x 1/4" in, 2x 1/4" out)
- Saffire PRO 24 (coax optical 1in 1out, standard optical 1in, 2x xlr in, 2x 1/4" in, 6x 1/4" out)

Finally, I have a spare PC which could run a server with one of these plugged in. I've looked at things like Jack and PulseAudio but both seem to be relatively old now (as well as describing themselves as "in development" - which to me says "abandoned"), and a lot of google results for guides with them are pretty dated... but I feel like this spare PC could be of use.

What are my options here?

 

[MidnightShadow]

Sooo... I'm no audio expert, but I believe the only way you're going to mix all that together is going to be with an audio mixer, which is going to require a PC. However, you said you want to still use it with the PC off. So, I don't think you're going to be able to do what you're asking. A good home theater system will let you switch from one source to another, but not mix them. A mixer on a PC will let you combine sources to a single output, but it has to stay on. You're going to have to make some concessions if you want anything close to what you're asking.

Unless somebody else knows something that I don't...

 

[Fureniku]

Sooo... I'm no audio expert, but I believe the only way you're going to mix all that together is going to be with an audio mixer, which is going to require a PC. However, you said you want to still use it with the PC off. So, I don't think you're going to be able to do what you're asking. A good home theater system will let you switch from one source to another, but not mix them. A mixer on a PC will let you combine sources to a single output, but it has to stay on. You're going to have to make some concessions if you want anything close to what you're asking.

Unless somebody else knows something that I don't...

Which software would I use for in-PC mixing? As I mentioned I do have a spare second PC that could stay on and out of sight - I just need to check if it'll be up to spec