The power supply that is in that case will provide more than enough power. According to NVidia's Website, the GT610 only needs a 300W PSU so the 450W should be fine.
Since you are planning on doing a lot of multimedia editing, the computer is going to be generating a lot of heat and the case you have selected is not very good at dissipating heat. It only has one fan on top and just a few vents on the side and back for passive cooling.
If you could fit another fan inside the case to push heat out, then you could use this case but you should think about getting a case with a bit more vents and another fan or two.