Pros: Good if your onboard current gear or onboard audio is of lower spec than the alc889
Cons: Not worth it if your current gear or onboard audio is to spec with the alc889 or better
Using WASAPI, ASIO and onboard stock drivers yielded the exact same result. Same sound quality and same sound coloration. Unless you are suffering from serious EMI and static noise then these dont really offer any improvement at all.
Just control the volume/output of the desktop or laptop to not damage the headphone drivers.