Originally Posted By: roundcallI really like the Tactical Inovation lowers, they have a couple extra features that most other lowers don't have.
http://www.tacticalinc.com/t15%E2%84%A2-forged-precision-machined-ar15-lower-receiver-p-1080.html
The detent capturing feature is nice as well as the tension screw for the upper. For $100 it saves you the labor of tapping the detent hole. Good link.
To the OP, I would think that as long as the lower is mil-spec (and I believe they all are with the exception of Colt and their FCG pin holes), any lower will do. If you plan to, or think you will, resell the rifle then get a name brand. I've had people look at me funny because I had a SAA lower or a Superior Arms lower vs RRA or DMPS, etc.
Hope this helps.