In reply to Sabilly1:
> I wanted to photograph wildlife mainly, but I thought the 70-200mm could have achieved the same with the teleconverter.
It worth thinking what you mean by 'wildlife'. There's a massive difference between (say) a Cettis warblers (very small, very shy) and (say) Humpback whales from a boat (very big, very curious). For the former you'll really need a *minimum* of 400mm on APS-C. For the latter a 70-200mm is more than enough (but you'll want water - or whale snot - proofing). Wildlife is a very broad subject!
Also you have to consider whether you're shooting a decent light or at dawn/dusk. In the latter case you really need a reasonably fast lens - bigger, heavier and more expensive (e.g., f2.8) than if you're only shooting in good light (e.g., f4).
Finally, if you're unsure, consider hiring a lens and playing with it for a few days. They're quite expensive, and you can't beat actually using one to see if it's worth an investment. My wife wanted a birding lens and tried a 600mm (on APS-C): Non-starter - couldn't hold it for any length of time!
Post edited at 12:57