Here is a handy add-on you can check out if you want to do less post-production on captured videos. Rather than try to facilitate the enhancement of 5.1 surround sound, the Holophone PortaMic 5.1 allows you to capture quality audio right on.
The Portamic is powered by a 9V battery which is good for use for up to 3 hours. It also has an onboard hardware that encodes Dolby Pro Logic II. The Holophone PortaMic 5.1 costs a steep $600 and may be limited to the ones who can spare a couple of bucks.