Looking to buy a decent receiver and 5.1 speakers and sub for living room..20 x 20...all my wiring is in the walls pre-wired f

Since your have in wall wiring in wall or ceiling speakers would make a neat installation.
I would suggest Paradigm or Revel for the speakers and Paradigm for the subwoofer.
For receiver Marantz offers excellent sound quality and a three year warranty.