Yeah agree with others, what role do you want to use your AR in CQC, long range etc. I myself like the Vortex products. Also the Primary Arms optics seem solid also.
Just going to shoot at the range. Probably a red dot can't think of any need for a magnified at this point. And I'm not sure on price range because I have no knowledge of optics but definitely want to get one that's worth the money. Not afraid to pay for quality.
Another vote for Aimpoint T1 or T2 if you have the cash. If not, another vote for Holosun. My son's Holosun ran just as well as my T2 last month at Valor Ridge, shooting from 5 to 300 yards, mud and rain.
If if you decide on magnified, check out Primary Arms stuff. I love the ACSS reticle, I have both the fixed 5x and 3x prism scopes, which can best be described as low budget ACOG's. Lots of people dig the 1-6x. All three are under $300.
If you are on a budget and looking for a solid red dot, the Primary Arms Advanced Micro Dot will suffice as well as the Holosun 503C. If you are not on a tight budget, get an Aimpoint like others have suggested.
Vortex Strike Fire. I have several and they run very well. Half the money of an Aimpoint.
If you are not jumping from a hovering Helo into a jungle and engaging the enemy the strike fire will fill your needs if a red dot is what you want.