Hi tacyos,
The power supply requirements are listed at newegg under specs, I'm not sure where you are wanting to buy it at.
You may not need to replace your power supply. If you can find out what your current power supply is and how many watts it is, usually around 500 watts is good enough depending on what else your computer is running. And you want to make sure you have the needed connections on the power supply unit.
What card you get is going to depend on what size tv you are going to be running it to and what you are going to be doing with it, such as games, movies, etc.. I think you should be able to get a card under a hundred dollars if you aren't playing games and the tv isn't over 30 inches.
It just all depends really. If you have more questions please let us know.