Yea you should get a dedicated graphics card for mild gaming/video editing. When looking at video cards you have to keep in mind what kind of power supply you have. The faster the card the more power it will draw so you will need a better power supply. AMD 7750 is a good entry card as it doesn't require additional power if your current one has a low watt rating. If your psu has a 6 pin pcie power I would suggest going with a 7770.
I have a Corsair 430W picked out, and I noticed that both cards ask for at least 400W, so I'm guessing I'll be okay? Thanks for the advice though.