canon 70-200 mm L f2.8 + 1.4 TC image quality

So I am going to get a 1.5 TC for my 70-200 mm and was wondering if it would have any drastic negative effects on the image quality.

ps. if this question has already been asked than feel free to delete the thread and direct me to the other thread. I did search but couldn't find one.

The 1.4x TC's do not do much to IQ, although they do effect it some... I like to stop mine down just a hair to f/4.5 or f/5, but it looks great wide open which is where I usually use it most. The 2x TC's are a different story and effect them pretty heavily though ,from what I have seen/read. Never owned a 2x, though.

I've seen a good 1.4x slightly kill the IQ of a cheap lens, but I've been mostly incapable of noticing any image degradation when pairing said TC with a higher-end lens like the 70200 2.8.