How do you best recommend doing this? And can I get it from the 10.5.8 update instead since that might be newer?
I'm using the integrated soundcard.
Yes you could try the 10.5.8 updater. Mount it and then open the .pkg file inside it using Pacifist. The files you want are the ones with GeForce, NVDANV, NVDAResman or NVSMU in the filename.
You could try disabling your soundcard, if you're using some additional kext to get it running. I haven't tried the EFI-X thingy so I don't know how it works its magic.