All of those lenses are nice, but make sure you really want the 100-400L. At the short end, its performance is weak by L standards (and not great by "normal" standards). It is a heavy piece of glass (over 3 lbs) and a push-pull zoom. Certainly, nothing else covers the range of focal lengths as well as the 100-400L, but personally, I'd rather have a 70-200 F/4 IS and maybe a 300mm or 400mm prime, later. YMMV, of course, but deffo try out the lens (try to rent it for a day or two) before you cough up for it.
The 17-40L wins on full frame, APS-C, and APS-H sensors. It's also a "bargain" by L standards. I'd start with it.