It's only June.
Water-cooled cards are false economy. (They don't cool the Video RAM, for a start.) If you want to get a water cooled PC, get one ... either yourself or a custom build will ensure that all the performance bits get cooled, either by air or water (e.g. spot fans and Corsair's heat-spreader technology for their RAM).
Specifics: the DirectX10 performance seems to be dependent on the hardware architecture of the cards, so (surprise!) nVidia and ATi have different results for their cards again. ATi is not good with Need for Speed, for example.
Motherboards: you can either opt for a good, fast relatively cheap motherboard, or one that is more expensive and doesn't have any performance benefit EXCEPT that it implements technology that hasn't been adopted yet (but will be in the next few months). In other words, depending on the upgrade strategy, you either buy a cheap mobo and CPU, or an expensive mobo and CPU that you can upgrade later (without upgrading the mobo).
The next round of CPU technology isn't due for a couple of months, and the latest Core 2 Duo is dirt cheap and easy to overclock A LOT.
specifics shortly