I think the Walkabout will go down ti 2ohms comfortably, so even if I wanted to double up the cabs, I think it would handle it. I also have a Schroeder 212BMF, so not screwed x2.I have no idea why you thought you needed the 4 Ohm ... truth is you didn't, and you have also screwed yourself over in regards to being able to have a modular setup ... With a 8 Ohm walkabout combo and an 8 Ohm extension cab you would have been set, I guess you spent more than you needed to arrive at this conclusion. It is Okay, all of us make mistakes. Cheers.