Multiple heat beds

What is the possibility and materials required to put 4x 8"x8" 12v heat beds under glass to make a 16"x16" heated build area? What would I need as far as power supplies? I’m guessing 1 12v power supply wouldn’t be enough, but maybe 2 500w? Is it feasible or am I just stuck to printing pla or a small build area with a single build plate?

I’m gonna add at least 1 for now. As soon as I make sure the power supply I got from this shop will handle it.

Hardest part will be controlling them all at the same time.

http://m.ebay.com/itm/18-X-18-Heatbed-PCB-Heated-Bed-for-3D-Printing-/261374879832

Go with that