I've just purchased a new motherboard and graphics card, since I got frustrated with getting my prior equipment working:
GIGABYTE GA-MA785GM-US2H
LAN: Realtek 8111C
Audio: Realtek ALC889A
Video:
- onboard: ATI Radeon HD 4200
- PCI-E: Galaxy nVidia GeForce GT 220 1GB 128-bit DDR2
(Yes, in hindsight I realize now I definitely should've gotten an ATI card )

Plugging all this into my previous rig, I was able to boot my SATA SL partition, with VGA graphics and no ethernet and sound. I did some tinkering with the config and got:

• Ethernet is recognized and I can assign it an IP address, but it won't connect to my router. I saw a forum reference to something called "RTG" for this chipset, but I have no idea what that is.
• Both IDE and SATA drives seem to be working fine
• Sound is recognized as "Intel HDA" but crackles badly after a while, and the system froze when I went into Prefs->Sound->Input
• Can't get any better than basic VGA graphics. I generated a custom EFI string for the nVidia card using OSX86Tools, but with this string in Boot.plist, the system reboots itself immediately as graphics mode starts up during boot

Any suggestions on what kexts/strings to use?