My iPC OSx86 10.5.6 Universal install on my Asus P5K with Nvidia 7800gtx oc went fairly well. My two issues are no sound, poor video (poor resolution and iMovie does not run becuause it does not run) and intermittent USB mouse and keyboard on power up.
My driver selections are:
Asus P5K - StageXNU Universal Kernal
Nvidia 7800gtx oc - NVinject 0.2.1 256MB VRAM
Chipset - Intel ICHx Sata Drivers
Audio - AD1988 (Asus P5K) you would think this would work
LAN- Attansic LI Ethernet
Apps - OSx86 Tools Utility

If anyone can help it would be great. I'm on the verge of giving up.

To get your sound to work you need to use Taruga's HDA Patcher.

Try searching for it on InsanelyMac, and also I think iPC even include it in the list of applications included on the install DVD.

P.s dont select the XNU kernel... just leave the kernel boxes blank as then it will by default install the vanilla kernel which is much better and compatible with ur setup.

Your graffix might be bad because of what card you have... typically the 7000 series dont have as much support as the 8000 series. However try installing the NVKush driver instead of the NVInject as this will have better support for your card I think.

Whats your progress with the Video? And whats your audio chipset? did you check any of the guide out there for you mobo? and like maracous said, you dont need a patched kernel, install vanilla man