James,
Few of us have the perfect setup. My left speaker is squeezed behind a sofa arm, so i built some crappy stands to raise them to the point that all drivers are shooting over the arm. My center is under my HDTV. Could it sound better if I had the ideal situation and placement? Probably, but It all sounds great just as it is. Just do the best you can and don't worry about it. As far as using the M60s in your space goes, Spiff may be right that you don't NEED it. But, if you want it, go for it. I sit only about 8 feet from my front 3 speakers. It all works just fine. Do the best you can do and don't worry about it.
