The tuners don't actually display tv. That's the remit of your graphics card. The tuner card only receives and decodes the digital/analogue tv signal for your GPU to display.
I'm using the Leadtek DTV1000T with DVB software, displaying on a 19" widescreen monitor via a Radeon X1950Pro . It's good. Your GPU should manage HDTV @ 1080i quite easily, provided you've got a decent reception/cable.