It is pretty exciting getting this far.
I am not sure if I am overlooking anything but I
cannot seem to find a method for a fresh
reinstall from scratch for snow leopard. Does
the hard drive need to be reformatted to remove
the original install? (sorry for the noob question)
if you are gonna do a fresh install, follow the guide you used to install in the first place.
when it mentions going to disk utility in the installer, click on your hard drive and erase.
itll format the drive.
then continue the install.
with the sound, were you using a dsdt and select alc8xx and applehda rollback from multibeast?
My Z68X-UD3H-B3 rev 1.0 (f9) is up and running 10.6.8 with motherboard sound, so it is ( or should be ) possible. As samisnake stated, you will need to install alc8xx and applehda rollback from multibeast after the update to 10.6.8 and then rebuild caches and repair permissions ( assuming you are using a DSDT ).
I had problems even installing BIOS f8 ( from f3 ), the process seemed to take forever and then would not validate. I even downloaded f8 from other GigaByte sites around the globe with the same result. I did not have any issue updating to f9 though. If you do change BIOS versions, remember to update to the matching DSDT.
If you have a spare drive, do your clean install to it of the basic 10.6.0.or 10.6.3 and then go back and boot from your current drive and do the update on the new drive to 10.6.8, followed by the HDA rollback etc and the cache repair ( and MultiBeast install that includes the Chimera bootloader ). I find it much easier to not do surgery on yourself i.e. I try to do my modifications/builds on a drive other than the one I am booted from. Just MHO.