What type of power supply do you have. If you have a generic supply you might want to have more than 300 Watt PSU, if you have a quality 300 Watt PSU you should be fine. Case fans and led's don't take much power to run. If you had another hard drive that would be a much bigger problem. If I am not mistaken the Ultra FX5200 needs its own power, my FX 5200 runs from the mobo.
My advice is if that it is a genric 300 Watt PSU, rip it out of the case and get yourself at nice 350 Watt PSU (See post on good versus bad brand names for PSU) If you have a 300 Watt Enlight, Antec, Sparkle you should be fine. With very few exceptions, if your PSU ends with "max", through it out. The link for that discussion is here
PSU - Good or Bad