@Baggers82 

You can use two TP-Link powerline adapters, such as TL-PA7017 KIT. They should work together with Deco E4.

Powerline link is very dependent on quality of electrical wiring and what is connected to it. You would not know if powerline will work at your place until you try. I would suggest getting just powerline adapters first and then use one of E4 you already have to test the quality of link.

If everything works, you can now get additional E4 unit.

  @Alexandre. 

Thanks for the reply. So if I bought that kit and it worked, how would I configure it to extend the deco network into the office?

Would I plug one Powerline adapter into the main E4 unit that's connected to the router? Then the second poweline adapter in the outside office with another E4 unit plugged into the poweline adapter?

Just trying to gety head around how it would all be wired up.

  @Baggers82 

You can connect powerline adapter to Main Deco, but you can also connect that powerline adapter to any of Satellite Deco in the house. If you find that powerline link is better when in house adapter is near Satellite Deco, connect it to Satellite Deco.