Personally, I see step one of this build as figuring out what is going into the lower and then buying it. Here goes nothing, please stop me if any of these parts won't fit together or if you see any parts that can be replaced with better parts that cost about the same.
-Bushmaster XM15 E2S Stripped Lower
-DPMS Lower Parts Kit
-Hogue Monogrip pistol grip
-ACE ARFX skeletal stock
Basically the concept I'm after is a 20'' AR15 rifle that somewhat resembles the SPR the special forces are using as a counter sniper rifle. I plan on attaching a A3 flatop upper, so if you see any issues with this please chim in. Thanks again for your help, this website is really an awesome resource!!!
P.S.- I looked up the firearms laws for my state (IL) online and it turns out I have to apply for a card idenifying me as a firearm owner in order to get my hands on a lower receiver. I downloaded the application, and it'll be in the mail as of Saturday.
If anyone knows the turnaround for this, please chim in, so I can give myself a timetable of when I can start building.