If you look on ASUS website, the only difference is that P5Q-E, it says
1.
"AI Audio 2 creates a virtual center channel that expands the overall
sound field without introducing a picket fencing effect. Preserving the
dialogue or solo performances with downmixing from multichannels will
allow you to experience true-to-life high quality audio."
2.
"Enjoy high-end sound system on your PC!
The
onboard 8-channel HD audio (High Definition Audio, previously codenamed
Azalia) CODEC enables high-quality 192KHz/24-bit audio output,
jack-sensing feature, retasking functions and multi-streaming
technology that simultaneously sends different audio streams to
different destinations. You can now talk to your partners on the
headphone while playing a multi-channel network games. All of these are
done on one computer."
In addition to the Noise filtering.
P5Q-Pro only lists the Noise filtering