Ok, I've been reading alot about Eotechs, and still cannot figure out which would be the best for my AR-15 flattops. Have been laboring over this decision for months and just want to get one! Didn't like the sight picture with the XPS, returned it. Considering just going with the 512 or 552. Not sure I really need night vision (am not military or law enforcement). Guess it would be nice to have the option though. Would like to have magnification in the future. The 557 appears to be specifically made for .223, but has the 7mm raised base. Is the raised base necessary for a flattop or is it just a preference/comfort thing? Have a 16" flattop with adjustable stock. Also have a 20" flattop with A2 stock. Would like to have Eotech to swap between the 2, and eventually save the money to get an ACOG for the 20", and leave the Eotech on the 16". Any suggestions?