It sounds a bit too far back to me. I would get close to equilateral triangle for good imaging, as I've found imaging is degraded as I get further from the speakers. The trade off is that you'll lose bass reinforcement if neither you nor the speakers is near a rear wall.
Try to get a listening chair that can easily slide forward. Also, unless the system is very bright, you could try the AudioPhysic trick of toeing in the speakers even more, so that an imaginary line from the speakers would intersect in front of you ... that helps to minimize side wall reflections.
Try to get a listening chair that can easily slide forward. Also, unless the system is very bright, you could try the AudioPhysic trick of toeing in the speakers even more, so that an imaginary line from the speakers would intersect in front of you ... that helps to minimize side wall reflections.