There are obviously conflicting views on this
My take is that distance matters for the mains and surrounds, while volume matters more for subwoofers. To earlier comments, sure it's only a few dB we are talking about but a few dB can translate into twice the amplifier power or twice the number of drivers in a speaker so it does make a difference...
In my case I was running M2s with a good sub and found them to be a VERY capable music system when I was sitting relatively close (say 6-8 feet) but as I moved further away and had to turn up the volume to keep the same SPL the M2s hit their limits pretty quickly. M60s in the same scenario had no problems playing cleanly at a "loud" SPL for a listener anywhere in the (13 x 23) room.
