Your wetek play could be setup as a tvheadend server, TVHeadend is a very undemanding program and can be run on just about any hardware. Not much of importance changes in it so there is little benefit in upgrading it once you have a working system. This means that all those old devices with outdated SOC’s but working dvb tuners can be relegated to TVH server duty and you can run your clients on a cheap modern box such as the x96Air which will provide all modern codec’s under CE.
I have to say, I’ve got a KIII Pro and I’m very happy with it. It does what it’s supposed to do without issue, and on top of that it has spare processing power to run a homeassistant docker instance + deconz (also docker) for zigbee control.
I don’t see what the problem is with integrated tuners. If I had to evolve this setup, I’d just consider leaving a device (in this case the KIII Pro) as a headless tvh server and converting it to a full blown linux machine (armbian?).
I think this split (headless server and media player clients) would be more efficient than having a device just for SAT > IP… I’d still be needing a headless server in that case and the actual media playing devices, only now with an extra widget.