Re: what is EAX?
EAX (Environmental Audio Extensions) Sound card functions that reproduce the reverberation effects heard in different environments. Developed by Creative Labs, EAX provides an extension to the Windows DirectSound and OpenAL programming interfaces.
EAX ADVANCED HD adds Multi-Environment, which renders the sounds in multiple environments at the same time as you walk past a room with a different environment. It also incorporates Environment Morphing, which blends the sounds of two environments together as you walk from one room into another. Following are relationships between EAX and other sound interfaces in Windows.
Hope this helps.
Macbook Pro and Logitech z5500s. All you really need.