Whether you use AHCI or IDE won't affect your overall OC'ing results in terms of MHz speed achieved. There is a way to make it work but XP works hassle-free using IDE. I do know if you do an install as IDE and want to change it over to AHCI, there is a tweak for that but just remember either way won't affect what you get when trying to clock the system itself up.
It will improve certain things such as response time from your SSD.
Here's how it's done with certain boards but don't know if it works with your board or not - I've never tried to do a switch myself.