I tried upgrading my 10.5.2 Kalyway build to 10.5.6 but I broke the thing so I started over with the iPC 10.5.6 build and finally had success.

Here's the hardware:
Asus P5W DH Deluxe Home mobo
Intel Q8400 processor
4GB ram (2x2GB)
Nvidia 8500GT 1GB video card
PS2 keyboard & mouse

Its a complete success except for no firewire, but I haven't looked at it or tried anything since I don't need it urgently. I'll fix it and post solution later.

Bios settings found via Google.

Install settings:
9.4.0 StageXNU Universal Kernel
Video under Nvidia: NVdarwin 1024
Chipset: Intel ICHx SATA Drivers
Audio under Legacy AppleHDA: ALC882 address 0
Ethernet: Marvell Yukon 88E8039/8053
Wireless: Realtek RTL8187/L
SATA Drive icon fix (new)
seatbelt fix kext
PS2 device support for keyboard and mouse
AppleSMBIOS-27 rev3 Mac Pro (the first mac pro choice on the list)

Then add any apps you might need. I recommend OSX86tools.

All works out of box with these settings. Only thing not being recognized is OB firewire, Sleeps and wakes good. Gotta wake from power button. System profiler shows accurate except for ram reported as 0. Activity monitor reports complete ram, so just a reporting error. USB work, though havent tested speed yet. Video card fully supported including QE.

So I deleted the AppleHPET kext and firewire now works! I am one happy camper.

Yeh thats the trick, thats for sharing, surely will help other members

When I go to hook up a monitor via DVI the computer kernel panics. Guess I'll use the d-sub for now until I can carbon clone this thing and tinker some more. Sheesh, I suppose this is why peeps actually buy these things from Apple! There is something to be said for plug-n-play. Then again this thing was really cheap to build!

I'll keep chugging and post updates as they are worth sharing. Stay tuned....