the 200 is a nice simple design that seems to be pretty happy with extenders. the 2x-I is not the greatest piece of glass, but it's an improvement over a crop from the 1.4x with the 200. you need to watch out for front/backfocus errors with extenders on older cameras without micro-adjust - both my 1.4x (even after a visit to Canon which improved it) and the 2x have significant focus issues
sorry, you can't have my 200, not as versatile as a zoom but great for action in low light and about as sharp as anything Canon makes