red dots are better suited to carbine length. in my experience, the magnifiers add a lot of weight. you will be better off with a nice low power, fixed magnification scope. put it on a quick detach mount with some mbus gen 2 underneath, and youre all set on back up irons too.
another alternative, albeit an expensive one, is just to go with a nice trijicon acog. they are good for cqb and decent mid-range shooting.
Favorite range gun for the money - CZ 75B or STI Spartan V 9mm
Go-to carry setup - Walther PPS or PPQ in FIST kydex holster 1AK
Favorite semi-auto design - HK P7
"A Sig is like a lightsaber - not as clumsy or random as a Glock."