That's a good summary, CJS06, and is what I believe to be true. TG is correct in that my knowledge of the 5.56 comes from teh interwebz...like 90% of everything else I know about firearms, since I don't have the money or time to get hands on with the many firearms, ammunition and gear I would like to try.
As I stated earlier, when I purchased my M1A, I needed a rifle that would reach out long distances, possibly greater than 400 yards, and also function effectively at shorter ranges. The M1A meets those criteria.
However, since it doesn't seem I will be relocating Midwest anymore and am likely to stay in more close quarters areas, other platforms are starting to look more capable relating to my perceived needs.
I like the idea of a shorter, suppressed rifle where I am right now. I am almost always in places with lots of people, in towns or cities, with the longest sight radius being 50-200 yards, tops. In my mind, without crunching all the numbers, selling my rifle, ammo, gear, etc. should net me $1800, which should enable the economical purchase of a .300 Blk pistol, Sig brace, ammo, and some sturdy but cheaper mags for it. Then depending on if I can scrounge up a little more dough, perhaps a tax stamp and suppressor down the road, since I like the idea of being hard to locate if I need to use a rifle.
These are also just initial thoughts on the subject...I'm not sold on the switch. It would be a pretty major undertaking.