Intex is a generic PSU brand and it can't be much trusted.
It delivers 18A on the single +12V rail, which looks okay.
Also, you have a G31 chipset which has a PCIe 1.0 slot for the GPU. Since the HD 6670 is a PCIe 2.1 card, it may have some issues with compatibility. A BIOS update could fix it, but it doesn't always do the trick.
I just checked Gigabyte's website, looks like it could be compatible, but do note that there would be a limiting bandwidth, so the HD 6670 wouldn't be running at it's maximum potential. http://www.gigabyte.com/products/product-page.aspx?pid=...
Assuming that is your motherboard.
But firstly, do check the version of BIOS that you are currently running.