Oh you have more than enough. I only had $100 and I got everything I needed...but then again I got mine off of ebay...

To check how much power you have, shut down your computer COMPLETELY! Unplug your the black cord in the back of your computer for safety reasons. Take off the side of your computer and look at your Power Supply. There might be something that says like 400W or 550W or something.

And while your looking, make sure you have a PCI-E slot. You should have one if you got your computer 2-3 years ago.