i use Miglia's Alchemy TV PCI card (g4 version with FM tuner) on a dual 533 g4 (10.3.4) and it rocks. much better quality than any USB TV solution. also has composite and s-video inputs for capturing from an external source (like VCR, DVD etc). picked it up for less than $150.
i can watch tv in a window (640x480,320x240,160x120) or full screen.
normally i just have a small window (320x240 or smaller) sitting on my desktop. great for watching hockey games while you work!
and the FM tuner is a bonus too! however, the G5 version of the card does not have the Fm tuner.
hope this helps.
shake