Lens for Yellowstone trip (or other wildlife viewing excursions)

You've got a great kit there, and you might use one of the 3rd party 1.4x TC's if you get really adventurous.

Basically, anything that is too far away for your 70-300 L plus a TC is too far away for anything better that is readily portable or affordable (there is never enough telephoto for distant wildlife unless you're going to park yourself in a blind for hours with your kit on a tripod).

Otherwise, as the others said, enjoy the park - it is totally amazing!

--
- Woody -
Equipment: Enough. For now.
Quote: 'The only thing some people will believe is their own eyes. But in the realm of the quality of a printed image, is there really anything else that can be believed? '