That wattage should be just fine. You really only need to go higher when there are multiple hard drives(or other components/fans/etc.) drawing power. You will want to consider the interface to the motherboard there are a few different kinds. Just snap a pic of the power supply interface on the motherboard and take it whereever you intend to buy your powersupply.

Or you could look up the specs of your current motherboard and take them in as well.

Also be sure that the new PS has enough auxiliary power feeds for all the devices you intend to power. Like hard disks floppys and optical devices.