I know you were, sorry. My comment came out more terse than I intended.
A 500 does give more reach, no question of that, but it really isn't as much as you think. The first shot below is with my 150-500 at 500mm. The second is with the same lens and a 1.4 TC, for 700mm or a difference of 200 (same as a 300 to 500). They were both shot at 60 meters and are uncropped
My TC is a Kenko PRO 300 AF 1.4X DGX converter and it does work pretty well. Those aren't the best shots I've taken with it, they are just the only two I could think of that had roughly the same shot with and without the TC. To be honest it works a lot better on my Nikkor 70-300 than on my Sigma 150-500. On the 70-300 there is very little loss of IQ, but it does cost one stop of exposure. Unlike some cheaper teleconverters it does properly report the aperture to the camera.
If you want to play with them, come to Nashville and we'll go to the zoo or the duck park and you can shoot both to your heart's content