Is 500w enough?

Ultra LS500 Lifetime Series 500W Power Supply, I have this from an older build

This is what I'm planing to build
Cooler Master RC-932-KKN5-GP HAF 932 Advance Full Tower Case
GIGABYTE GA-Z68AP-D3 Intel Z68 Motherboard
Intel Core i5-2500K 3.30GHz (will overclock to 4ghz at least)
XFX GeForce 9800 GT 512MB (already own, from older build, eventual upgrade)
2x4gb DDR3 ripjaws (already own)

Is 500w enough or should I buy a new power supply?

Although it is not a high quality PSU, it would be enough for your present planned system. Whether it would be good enough for an upgraded GPU would depend which GPU you were upgrading to.

32 amp (advertised) 12 volt rail is a little weak for a modern 500 watt PSU. Plus it has only one PCIe power plug.

Yes, I know you can use a molex -> PCIe adapter, but many of us try to avoid doing so. Better to get a PSU with all of the cables you will needs.

Here is a pretty nice 600w modular power supply from PC Power and Cooling for $59 after the rebates. Hard to beat at that price. Gives you the head room to upgrade to any single graphics card you want to in the future.

http://www.newegg.com/Product/Prod [...] 6817703036

The 500w model is also on great sale at only $49 after rebates. This will handle anything except the highest end graphics cards. Also is modular.

http://www.newegg.com/Product/Prod [...] 6817703035