Since those 2 outlets are handling all the power extension units, you're probably fine in adding more physical outlets. Basically you're expanding the opening, getting an "old work" style box, and where the line feeds off one end to the next outlet in the room, you'll undo those, add wires over to the new outlet and then feed off the new one to the next in line.

If you don't want to tear up the walls ... there are systems that have a "starter" box and then you run these flat plastic wire holders with covers around to wherever you want another box.