Hey all, I'm looking at purchasing an Eotech sight for my Ar15 here soon. I'm just curious...I see many different models, and the most expensive is the 552 I believe. What advantages does the top model have? If it is just on a gun that I target practice with and play around with, do I really need the top model? Just don't want to waste my $ on something I don't need, but then again, I DO want something that is high quality. Thanks!