[Darryl Ramm]

Surround sound is a *software feature* in Pro Tools HD, it will wotk with any interface that Pro Tools/Pro Tools HD will work with. It does not need to be an Avid interface. Obviously you need enough actual physical IO do whatever you want.

You can also hack your way into multichannel sound with regular Pro Tools, no rocket science there, and you can find how to do that with a Google search, but yes if you want to make it close to easy then you are going to use Pro Tools HD software. The other option is to use just about any other DAW, many of which include that capability in their much lower-priced products.