I think your PSU should do fine. I check this http://www.overclockersclub.com/reviews/sapphire_hd6670... and system Power consumption is all below 300W. But I must to know what brand is the PSU. And, do your Motherboard support Pci-E 2.0? If no, then it is better for you to get a complete new system because your motherboard will not support 6670. Your system is too old right now. I will give you the parts.