This sleep issue is really bugging me. I used iBoot and Multibeast to facilitate the installation of Retail OSX.
In MultiBeast I used a DSDT that Marlorn provided for another ASUS N50 user (attached below). In his post, he had some accroynms that was unsure of, I don't know if it was what patches he added to the DSDT or patches that still needed to be applied. I also used his smbios.plist he provided in the same post (attached aswell). Ah yes, chipset is ICH9M.
I am using the 10.6.7 Sleepenabler.kext from Nawcom (I think that's the name) and it works beautifully on another computer.
Whenever the computer sleeps, I hear the drives immediately spin back up as if it wanted to restart, but a hard restart is required in order to power up.