ASUS just released a BETA driver with EAX 5.0 support! To make a long story short, I am building a new system for myself tonight and will be installing and testing this driver. All I can say is that I am so happy I bought this card.
I received an email from ASUS recently about this development. Even though the driver itself is still in 'beta', anyone who's been bemoaning the lack of EAX 3.0 and higher support on the Xonar cards would do well to check this driver out. As a side note, it's likely that EAX 3.0-and-up processing is done in software instead of in hardware, as is most of the DSP for the CMI8788 chipset, so expect this to put slightly more load on your CPU than an X-Fi card, which handles this processing in hardware with its onboard DSP logic.