To answer some of hte questions...
Aimpoint magnifiers arent cheap. You should be able to find them online for about $470-$480. The flip mounts you see there are not cheap either. About $220 for that. As you can see, thats about $700. You can use any 30mm ring that lines up with your Aimpoint for the magnifier, but I swear, I really think this Samson flip mount MAKES the combo. It is really pretty great I think.
If I were to just have an Aimpoint + Magnifier, or a ACOG, I would probably go ACOG. With the BAC, the ACOG does the CQB role nearly, if not as good as the Aimpoint, but the ACOG does the magnification end of the job MUCH better than the Aimpoint + magnifier. Magnified image is clearer, ACOG has a better, much more USEFUL reticle (bullet drop and ranging).
The dots in the Aimpoints are 4moa, or, if you get the new M3's 2moa or 4 moa. The magnifier makes the reticle appear larger, but it is still either 2 or 4 moa (depending on which Aimpoint you go with). People dont seem to understand how thats possibe, but think of it like this. If you are looking at a 6 foot man downrange, and then you look at him with a 3x scope, he doesnt grow to 18 feet. He's still 6 feet. Same for the reticle. If its 4 moa unmagnified, it doesnt grow to 12 moa after the 3x, it just looks bigger (just like your target).