I've got a gigabyte EP45-UD3L, with OS 10.6 you can use a DSDT as part of your bootloader so you don't have to hack your BIOS. OEM DVD requires a USB stick or kakewalk CD to load up, but after that as long as you've got an nVidia video card its quite straightforward... just download the relevant kexts.
You can use an ATI card, but not all are supported. Also if your card's not supported you can still run in VESA mode, but then you won't have hardware acceleration or OpenGL.