Originally Posted by Eeyore
Best advice I can give you is to get a base gun and make it your own. I've bought so many accessories and have discovered that the don't fit the style of my play or that they arn't comfortable for me. If you get a base M4 you can put the stock, barrel, flash hider, optic grip that you want.
With that in mind, I'd recommend either a King Arms, Classic Army, or G&P M4.
You have quite a few different guns on your list. What specifically do you want? Don't know? Then go to a few games and rent until you find out.