Good advice. I think in REW there is even an "average" tab where you can select which measurements to include and view an average of the responses. You could take 3 measurements, one in each spot on the couch, and work on that.
I know that in my rectangular room, speakers firing long-ways into it, with the sub in the front left corner, the middle position is average. On the right side, higher sub frequencies are boosted but lower are down, and on the left side of the couch, higher sub frequencies are down a bit and lower frequencies get a boost. So my middle seat is already kind of an average.
