I just put a SS 6x42 on my M1A. My budget was $600-$800 and this was by far the best optic in that class and it only cost $300.00
http://swfa.com/SWFA-SS-6x42-Tactica...pe-P53711.aspx
My next scope for med-range AR15 is the Weaver Tactical. I have always like Weaver scopes and while I have not seen this yet, the reviews are glowing.
http://swfa.com/Weaver-Tactical-Rifle-Scopes-C1815.aspx