How do I know if this GPU is compatible?

Overstew

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Aug 3, 2011
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How do I know if this'll work on my computer?
I've got an HPE-300z model. The measurements of the shell is 40x40x18 (LxHxW, measurements in cm). I currently have an ATI radeon 5570 HD but am upgrading to ATI Radeon 6850, and that needs a higher power supply. So, I found this.

Power Supply (6-pin compatible + 500 Watts+)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817171052

I read something about it needing a 6 pin connector to work? but this one says 6pin for GPU and 4 pin for main power? Is that right? I'm going to have Bestbuy do the installation but I want to make sure it works before I purchase the graphics card and power supply. I asked Bestbuy over the phone and they said they can check if I have all the parts in the store.

Please help! I really want this graphics card! B)

If anyone else has a better price/performance ratio for graphics card, let me know! I'm open to suggestions!