If putting together the lower is daunting, just remember a squid with no idea on the ar15 put the lower together. Instructions about online. As for manufacturers, Im of the mindset that they learned a long time ago to either make quality products, or get out of the buisness all together. As for getting one for $800, there are a few auction sites like gunbroker and buds gun shop that have a few for around what your willing to pay. You would be better off building your own though, buying used can be a crap shoot. The gun you get may have been a safe queen or a torture tested weapon. Good luck to you either way you go.
My way is not better, it is just mine, your way is not better, it is just yours.
Carry what your comfortable with, there is no "Supergun" Carry how your comfortable, open or concealed, so you have it with you when you need it