ah ok. well I guess my thoughts were with the 100-400 i could still get up to 800 if I wanted to for as little $ needed (with a 2xTC). I honestly don't know when I would shoot that length other than maybe a few sporting events a year. It would be fun to have but yes the 2.8 IS 70-200 would be the more logical choice because I could use it on a regular basis with the lower aperture.
eh, i'll give it some thought when I get back home from Hawaii. Sadly, I really only used my camera one day so far. I am having too much fun enjoying everything rather than shooting everything. Maybe I'll just have to come back again soon to shoot only (without the wife).