so i have this 500 watt PSU http://www.newegg.com/Product/Product.aspx?Item=N82E16817171031
athlon II x2 @4.0GHz and a 4890. i have to use a molex to 6pin to make my card work. i want to upgrade to a quad but im scared the the quad and the 4890 will suck up too much power. i could upgrade my Gpu and that would take less power, but then i wont have enough money for a new cpu. what should i upgrade in this situation? i have a max of $150 budget
Well you are in a bit of a pickle here. As much as I like Cooler Master I see the PSU is not 80+bronze certified. The PSU is the heart of any computer system so my advice would be to upgrade your PSU first with either a SeaSonic or even a Cooler Master 600W 80+ Bronze certified unit. Note: This is the Newegg Canadian site for these units.
http://www.newegg.ca/Product/Product.aspx?Item=N82E16817151106
http://www.newegg.ca/Product/Product.aspx?Item=N82E16817171068
Everything else can come afterwards. Perhaps you can save up some more cash for later and improve your motherboard and CPU but for now I really recommend the PSU.