It's been a few years since i last tried, but I was pretty satisfied with TBS PCI-e tuners [1]. Good linux support, stable, and you can get them with multiple tuners to stream/record many channels at once.
This is a route that I was planning to take on Linux, so it is disappointing to hear that this was your experience. Is it possible that HDHomeRun as the backend to Tvheadend is the way to go?
