Weatherproof and sports means D300, which is sealed and has best AF-system from mentioned cameras. Quite good in low light (though D90 is tad better) as well, though you have to take care with settings and exposure otherwise noise could be visible even in ISO 200.
I'm not sure that battery grip is needed with D300: it's 6fps without and 8fps with it (but then it needs another type of battery and charger), and adds considerable size and weight. Of course shooting with large lenses is little bit easier as well as in portrait orientation but still... I used D300 ca. 15 months and never missed battery grip (power kit set with grip + battery + charger cost here ca. 700 USD 8( , so this was also one reason not to buy it) .
Just trying to master potential energy conversion to kinetic...