SiliconDust makes HDHomeRunextend, which you connect to the mac via ethernet. It has two tuners. If you put it on your home network, and mac (or PC) can grab a tuner and watch. The $170 newer version is wifi capable.
I live in an area where half the stations are north and half the stations are south and omni antennas are not good enough. So I have two high gain antennas, one connected to one tuner and the other to the other, and then pick the tuner with the best signal for the station I want to watch.
VLC plays shows, but I use MythTV for its added DVR type functions. Works very well once you get it installed.
Dunno if anyone makes "Inexpensive" PCI card tuners that work well in a MAC, but I haven't been shopping for over a year.