What service are you going to use on the Internet? Simply getting a Roku box for $60 is the way to go if you are going to use any of the services it supports.
http://www.roku.com/
If you are really into iTunes, then an AppleTV will serve your needs much better for about the same price as a video card.
But, if you insist on a new video card for the purpose, it's hard to make a recommendation without knowing more. For example, do you want HDMI output to your TV? Do you want it to replace your existing card and support three output devices, or are you going to add it to your existing card? Also, many TVs are really problematic connecting to Macs.