DSDT is recommended if you have problems with DVD writer - it fixes it all. Anyway, in general it's better to use it since your computer looks more mac-alike for Snow Leopard.

Are you sure that you don't have any other kexts for graphics?

PS I checked your extensions folder - it's a total mess, you don't need any sleep enabler or NullCPUPowerManagement. Please follow my instructions and replace it with my files from post above, then tell me if it worked.

In case you can't find my files: http://rapidshare.com/files/40743101...4_-_Backup.zip