JV,
I like the Sanus mounting brackets: http://www.sanus.com/us/en/ I have installed the big ones and little ones and as Reno said, it's better to fish the wires to a real box. We usually rough the wires in behind the drywall and fish them out after we have marked the location on the TV and the bracket. In my area, most people use a cable box so I rough the coax to the cable box location and then run coax and/or HDMI cable to the TV.