Well simply put, I saw your post, saw that you were going to change the graphics, saw that you have not yet posted a dsdt and I decided to wait to hear back from you once you had adjusted your hardware.
We will need you to get a nice clean dsdt.dsl for us to look at, and we'd need to know what you want to fix in it, if anything?
I know of no dsdt patch that is going to help a system like yours off hand - your HD Audio device is AD1983HD sound chip according to the pci ids database - I know of nothing that will make that work natively, though VoodooHDA.kext might get it somewhat functional and is worth a shot, you might just be better off getting a usb audio device that works oob. You have no AHCI, and you haven't really told us what you'd like to patch in your dsdt or what you've done so far?
So without these details, I don't think any of us are really sure exactly how to help you just yet...