help in compresser size

I have a 5hp and 30 gallon and it can't keep up for any extended period of running. Air tools like impact I can run 2 or 3 lug nuts off and have to wait. It can't begin to keep up with my die grinder.

I'm looking at getting at least a 60 gallon, something along this line with a good air filtration system.

http://www.northerntool.com/shop/tools/product_200318461_200318461