Not really tvh-related, but I experimented with a multi-output USB sound card for surround, but finally just bought a second-hand Yamaha sound processor that has a 3-channel amp. With the sound card I had a separate, homebuilt amp based on LM3886. The Yamaha feeds the two rear speakers and the center one (purpose built to fit in the shelf below the TV) and the old Denon receiver feeds left/right. The subwoofer has its own amp.
For us, tvheadend if close to perfect. I just have one small gripe: With Finnish TV DVB-T, whenever I record, it will create a small seconds-to minutes recording before the film and another after. The message is "Source reconfigured". Other than that, just perfect. I can add recording from the EPG in OSMC, from the web interface or from TVHClient. The latter is what I use when I read the paper and check the programmes on my Samsung tablet (Recently upgraded to LineageOS 11). I just switch back and forth and add stuff I find interesting.