Very nice. What lens were you using? The Kenko extension tubes allow autofocus, so I would get them over the cheaper ones. Also note they are only in a kit for $199 with a 12mm, a 20mm and a 36mm tube. The Canon 12mm is sold alone for $84. The product description does not state it, but I am sure theirs is compatible with the AF as well.
f/2.8 300mm II + 2xTC III. I will go for the Canon because I presume it is strong enough to marry a monster lens to a heavy body without snapping in two.
5D III, 7D II, EOS-M, Powershot G3 X, 300/2.8 II, 1.4xTC III, 2xTC III, 70-200/4 IS, 24-105, 15-85, 100-400 II, Sigma 10-20, EOS-M 18-55, f/2 22, 11-22