Thanks for the quick responses, and tips on where to purchase!
Unfortunately, I prefer not to use floor speakers. Mostly, it's a cosmetic issue, and the concern of them getting bumped and banged by. kids. However, I feel the 600Ms may be too small even for fronts.
Agreed. The space is 4ft from the screen to the seats, and the screen is 120 inches. I tend to seat in the last row further back, and even when guests are over the 1st row is always the last option.