I have just set up one of my Pi 2's as a tvheadend server with a win Nova T ministick USB tuner. It only took around an hour and works a treat (most of the time was scanning & scraping).
As my Pi3 is currently in use as a retro console I was concerned that the Pi2 would not be man enough especially as I do not have the mpeg2 license for this pi. I was pleasantly surprised, even recording one show and streaming a recording the pi was only using 80Mb of RAM and not much CPU.
I have a second tuner on the way but my question is. How many tuners can you run off a Pi2/Pi3?
I currently have 1 tuner and 1 USB stick as my hardrive crashed every time it spun up (need external power).