I would try it in both of those locations if possible. The nearfield location will provide more mid-bass impact at the main listening position, but the farfield location may provide better deep bass and improved results across different listening positions. Note that you can always put the subwoofer close to the front left corner (as viewed from the main listening position, ie. top right hand portion of the picture) but put it next to the couch so that it is not very obtrusive.
Pete - Hsu Research