Apple has released two updates since 10.6.4 which are 10.6.5 and 10.6.6.
These updates are just fine to be treated as 10.6.4.
If you are doing a fresh install, you can follow the Holy Hackintosh Guide using 10.6.6 instead of 10.6.4. If you are upgrading your current install, you can do that no problems. Just reinstall the AppleHDA.kext to fix sound after upgrading.
You can find the AppleHDA.kext in step 5 in the My Holy Hackintosh Build or just click here.
