Try experimenting with your existing speakers. If you go with extreme toe-in, you can effectively improve coverage. If the left speaker is aimed at the viewer/listener on the extreme right side, that listener will get a loud signal from the left speaker and will be off-axis from the right hand speaker (because that speaker will also be toed-in) -- this will provide some compensation for the difference in distance between the listener and the two speakers.
Back in the 1970s, the Leslie company (yes, the organ people) designed a speaker with limited dispersion for specifically this purpose. The limited dispersion reduced the amount of signal off axis, to have the compensating effect I have described above.
Back in the 1970s, the Leslie company (yes, the organ people) designed a speaker with limited dispersion for specifically this purpose. The limited dispersion reduced the amount of signal off axis, to have the compensating effect I have described above.