First of all, you are getting raped on your prices. At [url]www.sableco.net[/url] Reflex is available all day long for $289, the Comp ACOGs are $580 and the Aimpoint M2 is $390. Now that this is out of the way...
The ballistic limitations inherant in your 11.5" barrel or 9mm carbine kind of limits you to close range effectiveness. So keeping that in mind, I would probably skip the magnification of the ACOG. Even though it will shoot accurately out at distances where you might appreciate the magnification, the round will be pretty worthless at those distances.
That being the case, I would go with the Aimpoint on a GG&G Cantilever mount, backed by a ARMS #40 BUIS. Very quick and easy to use out to well beyond the range where your rifle will be effective (ballistically that is).