I currenty have a 420W power supply. I was thinking about upgrading to a Thermaltake W0014 Silent Purepower 480W with Black housing - Xaser Edition ATX 2-Fan Power Supply. What is the difference between the wattage in the power supply? Also, do you have to buy a specific type of power supply for your computer or can you basically buy any one. Does anyone have a Thermaltake power supply?