Which graphic card is best for hd video editing

Most modern cards handle that fine inclusive of the IGP on the I7. Just a matter of budget.

Complete specs please. And Budget of course.

I would try to get something like this:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

It depends on what software you are using. Many use gpu acceleration and you will be better off looking at the compatibility charts on their websites as different software depends on either CUDA and/or Open GL/CL. If you are using Adobe products, I suggest a 4 or 5 series Nvidia GTX card. If you have the cash, I recommend going pro with a Quadro or Fire Pro card. They are optimized for professional applications and usually give better performance than their consumer counterparts.