I think you need to go into high quality lighting mode to view the texture at its proper resolution when using a surface shader, or change the Textured Channel attribute. I've never understood this node. Playing with it now, I either get low res + transparency or normal res and no transparency in my viewport.
Are you using the RGB colors for transparency in that last image? It looks like it's working otherwise. From the same texture, you should attach outTransparency from the same texture node to transparency of the shader node. (by default if the tga has alpha as you mention earlier.) this is in the standard viewport. And do…