It sounds like what you want is a flat top model with removeable carry handle (A3-A4). The rear sight is mounted in the carry handle but you can remove it and install a scope in it's place. There are many models available in your price range. Look at Bushmaster, Spikes Tactical, BCM, Smith and Wesson M&P15, like I said, there are many, too many to list. I have heard of several people buying the S&W for around $650 lately but I don't know where they bought them from. I have no first hand knowledge of the S&W but I have heard a lot from happy owners and my Local gun shop owner about their quality. It would probably be easier to find something you like the looks of and then ask about a particular model since there are so many. Models to stay away from would be Model One sales, Olympic, just off the top of my head, again, I don't have first hand knowledge of those either, just have heard a lot of people say to avoid them. I have a Bushmaster Patrolman model and love it. It eats what ever ammo you feed it and has never given me a problem. It does not come with removable carry handle but they have plenty of other modes that do.