Rob, your research is impressive, but with the spec of the optical zooms (ignore Digital Zoom) the cameras you mentioned are not really up to aircraft or motorsport photography, if action shots are the game.
There must now be some of the older Digital Slr's on the second hand market at reasonable prices and six month guarantees. I know loads of guys who are on their third upgrade by now, simply trading in the older model after six months or so, when a superior model becomes available.
Being that it is a work tool, smug bastard here went straight from film to Canon 1Ds as I hate playing the upgrade game. It actually paid for itself on the first few jobs. It has now been superceded by the 1Ds Mk2 which is actually in excess of my clients requirements, so no tears there.
If a new Slr is outwith the budget, call around the Photo biggies for S/H I say.