depends on whatcha wanna do with it and how much ya wanna spend on it. i'm VERY LOW on cash now (work just cut out ALL overtime

no extra $ for us...) anyhow i personally like the small style scops on ARs, like a short scope... looks good, i've been looking at Burris stuff lately.. i like the 2x-7-35mm with the ballistic mil-dot...but thats just me...
BTW are you getting a A2 or A3...? i've got a Bushmaster A3 and tis freakin AWESOME!!!
Good luck.