I'm on an AR budget of between $599-$699. I've narrowed down my decision to: S&W M&P 15 Sport......PSA 16" M4 .......DPMS M4 I'm using this weapon for home defense and range plinking. Whats your recommendation as to what I should purchase and why. In time I will be adding accessories like a new grip, Pic rails for a forward grip-handle. I already have 2 optics for it. (Note: I do have 17- 30rd and 5- 20 rd mags.) Thanks in advance!