Others have intimated this but I think it needs to be stated forcefully: Canon teleconverters do not tend to fit third party lenses (or even most of Canon's own lenses, especially non-telephoto ones). They have protruding front elements, so the lenses they are attached to must have quite a deep recess at the back to accommodate them. I've not used this Tamron lens, and it's not easy to tell from cross section diagrams how much space there is at the back, but I'd want to be sure others have successfully mated it to Canon extenders before buying one. (You can of course use an extension tube, but that will impact autofocus speed, infinity focus, and possibly image quality).
Third party teleconverters will be more accommodating - I have a Kenko 2x version which fits all lenses I've tried it with - but they will not produce such good results (reflected in the price difference). Nonetheless, they can still be a good choice. It's worth stopping down the aperture a little if you use them, I would say, especially if the lens suffers from distortions/aberrations to begin with.