12 Ga in wall cable for your speakers is a very good choice. I used 14 Ga. for mine. In wall speaker cable is usually twisted within the sheath to prevent noise cancellation at audio frequency's, I see no need for shielding. How do you connect the shield anyways? I also see no need for Cat 6 Shielded cable. Again, how do you connect the shield? I have never used shielded speaker or Cat wire and have no problems. If someone here says there is a need for shielded wire, please speak up.
As far as in wall speakers, I am a fan of them for the surrounds. Less clutter in the room. I once stated that the surrounds are only for effects and was called narrow minded on this site for my views. I do believe the fronts should be stand alone speakers. Just my opinions, Fellow Audio Nut.
Hey, a new word, FAN !
(LCD - Sony KDL -52 XBR4) (Receiver - Yamaha RX-A1040)(Blu Ray - Oppo BDP-83) (PS3)( Comcast X1) Speakers (L & R - Paradigm Studio 20) (Center -Paradigm CC-470) (Surrounds & Back Surrounds - Paradigm SA-15R in walls) (Subwoofer 1 - Sunfire HRS-12) (Subwoofer 2 - Paradigm PW-2100)