Depends on what's on sale and what's in stock. A PSA model as you described can be had for $700-750 if you hit a sale. Or they may have a complete upper at a great price but no lowers in stock. It all depends. I hit their sale on my upper for $280 and charging handle for $15. BCG wasn't in stock, so I went with BCM. I got my stripped lower locally. YMMV.
Most of us who build end up with mixed parts and no problems. My PSA upper is on an ArmaLite lower and looks/works fine. Do enough research, dont buy junk parts and you'll be fine.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek
Last edited by Quentin; 11-08-2012 at 05:18 PM.