Not on your list, my favorite Airsoft, VFC Knights Armament PDW. Not an M4 but takes M4 mags. Needs nothing out of the box, very versatile, inner barrel if you want a bit more precision, you can change the barrel length at will. Folded it fits in a briefcase. Doesn't need optics, it's a natural, point and shoot. Little bit more expensive then your budget new, but a lot more for your money if you can wait
VFC Knights Armament PDW - YouTube