Now the C2 works just fine, I'm just getting really tired of a crappy case dangling from my TV and a Logitech Harmony that DOES work (through CEC I guess?). But the functionality is very basic, play and pause for instance don't work.
I just want a decent case which I can place under my TV and an IR receiver. So pretty much Wetek is the only option for a decent prebuild case which works with a remote. Slice devices aren't available here and from the Wetek line I only can get the Hub and Core, which are about 105 euros here (Amazon.de). That seems pretty expensive to me though. Especially because according to reviews it can't handle high bit rate 4K video, something that my C2 can do without an issue.