I know this thread isn't to critique your build, but why the 8500? Get the 8400 for ~$80 less and just do a minor OC to 3.16ghz. And also, 3x DVD drives? Why do you need 3 drives? Heatsink, try a XIGMATEK HDT-S1283. Its the top rated LGA775 heatsink.
But on to the power supply, Seems to me that you would be ok with a solid 600 watt power supply or more. If you go to newegg, a PC Power & Cooling PSU is always a great choice, try this one for instance: http://www.newegg.com/product/product.aspx?item=N82E16817703005