As scuzzycard mentioned, yes, but the bigger question is why would you want to?
Better off getting 2 1070s in SLI, or waiting until the start of next year to pick up the higher end cards from ATI if you want to go that route.
Driver requirements aside, the software you are using has to be programmed to utilize and SCALE all the GPUs, and most software (including games) on the market DOES NOT.
1st link gives a good explanation of performance comparisons.
2nd link gives a great explanation of acoustic and power comparisons.
Watch both and make an informed decision for yourself. If you decide to proceed, then list your specs, and power supply's manufacturer and model #, and we'll be happy to help you upgrade yours if necessary.