Thanks Jen for your review on the extenders. I'm getting similar feedback from reviews (1.4 vs 2)that I've been I'm researching. I agree with the your reasoning 'size & price' for my decision. 448mm at f4 should do the trick for my 'unexpected out of rangers'.
My 17-85 should more than do the trick for my wide angles, I'll have to experiment more, and move my feet. lol