Precision 3630 upgrades

I've decided its time to upgrade this beast its relatively new but the boss cheaped out when buying my question is that i read somewhere that if i want max out the video card with something bigger than whats currently installed im going to have to upgrade my current power supply curent power supply is 300W, N-SD, GOLD and the current video is Nvidia Quadro p400 what were doing with this is some basic video editing however things have rampped up and we are running into bottlenecks and its time to upgrade i'm thinking CPU as well an links would be helpful