FX Impact M3 bipod ?

Lower cost (non of these are cheap) and light weight - Magpul 

Really nice - Atlas BT10-LW17

My favorite but expensive - Accu Tac FC-5 G2

As far as other accessories I would recommend 1st the rail extension, then butt stock with monopod, with these I would skip bag rider and cheek piece. I have the Saber Tactical but i don't think you could go wrong with the Saber or Kraford & Lypt. A good bipod and either butt stock with a monopod make helluva a nice shooting setup.