Are you dead set on an AR? I have an FN FAL SA58 carbine from DSArms and it's great.
http://www.dsarms.com/products.asp?dept=8
Have you considered the bullpup Kel-Tec RFB?
http://gunblast.com/KelTec-RFB.htm
I did already get the receiver but i wish i saw that kel-tec earlier. Only reason why i decided on an AR platform is because of the lower recoil and availability of aftermarket upgrades. I've never shot a FAL so i have no experience with them but on that site, the price of those is around what it would cost me to build a very nice long distance AR anyway...but that kel-tec being as short as it is with the same barrel length is pretty awesome. It's also probably $400 cheaper then the AR. Have you ever shot one?