Any half-decent card should suffice, my own is a lowly Nvidia GeForce6600.
For PC to TV you will need at least S-video Out and Audio out sockets on Graphics card. But much depends on what connections are available on the TV as well.
Don't expect graphics on TV to be anywhere near as good as on PC though.
For TV to PC, you would need a TV Card, perhaps from the Hauppauge range of cards.