Hey welcome to the forums! You are at the right place but if you could first do a couple of things. First, you are not quite in the right forums. Don't worry, it happens(someone might be able to move it for you). This really belongs in Graphics & Displays > Graphics Cards. Second if you could please fill out the information in this post, that would be great and help us serve you better. http://www.tomshardware.com/forum/290969-33-advice-choo...
Now to answer your question, a good start might be getting an AMD Radeon HD 7750 or the HD 6750, but again fill out the questions and we can match you up with the right card. Important things to fill out is price range, usage, psu wattage/or system model(if ordered/prebuilt), and motherboard, along with current graphics/video card.
I need to replace my video card (desk top computer) and I'm not sure what to install. There are so many. I don't play video games, but like the underwater films etc.
If you don't need to play games and only need it for movies you could probably go with just the onbuild graphics on your mobo and if your monitor isn't too big. Just remove your graphic card and put the VGA/DVI/HDMI cable into the port higher up.