Finally going to get my 300mm but still debating on which TC to get. I've heard mixed reviews on the 2x TC and don't want to make the mistake of returning it to exchange for the 1.4x TC. I will be shooting a lot of High School Sports like Football and two seasons of Rugby here locally with of course a lot of Wildlife action too. I know the 1.4x TC will probably be all I need for Sports but it would be nice to have the 2x TC for Wildlife too. Getting both is out of my budget currently so I need to pull the trigger only on one for now. So my question is how is the AF performance with the 2x TC and 300 f2.8L IS V1 Combo and have you tested it on the 1DX Mark II? Found this image on flickr and it has pretty damn good sharpness for a 2x TC on a 6D but nobody talks about AF speed and will the 1DX Mark II drive the AF faster than previous cameras.