Definitely try it out first, as the quality of a teleconverter is impossible to predict! as it's entirely dependent upon the lens it's matched with.
Typically, a 1.4x teleconverter is almost always a useful tool, whereas a 2x converter is only useful when it's nicely matched to a lens.
The final photo is the combination of your lens and the converter... most of the time the converter will amplify the already existing issues with your lens or introduce new problems, (softness, CA), however in rare and random circumstances I've actually encountered teleconverters that improved image quality--I'm guessing that whatever optical flaws the converter had were corrective to the flaws in my lens--like a eye-glasses.