I successfully installed Snow Leopard on my Asus P7P55D using this guide:
tonymacx86's P55 Hackintosh Blog: Install OS X Snow Leopard Directly from Retail DVD Using Chameleon Boot CD for P55 Motherboards

With this guide, Snow Leopard runs with the 64Bit kernel (i think). Everything is working so far, also sound, ethernet and graphics.

But I still have one problem: When I connect my iPhone, iTunes does not recognize it at all. The iPhone is listed as an usb device in the system profiler, but iTunes does not show it.
When I connect the iPhone, I get error messages in the console that IOKit6.0.kext (a PlugIn in System.kext) does not fit to the kernel architecture x64 and thus cannot be loaded.
Does that mean, IOKit6.0.kext is 32Bit?

Perhaps somebody has/had the same problem, or somebody can give me a hint how to solve this?

Thanks in advance!