The problem with that design is that the Encores need to have at least the long edges (these would be the sides when standing up) rounded over. You can round over all the edges if you want, but at least the sides (top & bottom on the center channel) need to be rounded over.
Rounding all the edges poses a problem for veneering. You can't bend veneer over more than two planes. There are a few ways I know of to get around this. The one that has worked best for me isn't really veneering, the pieces are too thick. It would more accurately be called laminating hardwood to MDF. With this method, the hardwood (walnut in your case) needs to be thick enough so whatever size radius you are going to use doesn't cut through it. The hardwood is laminated to the outside of the cabinet. Be sure to take the thickness of the hardwood into account when building the box. Flush trim the pieces of hardwood to the cabinet as you go. Now you can roundover all the edges and the color and grain will flow and look right.
The problem with this method is getting the pieces of hardwood to the thickness(s) you need. If a person has the ability to joint, plane, resaw, and thickness sand they can make the hardwood pieces themselves. If not, there are usually places that will process the lumber for a fee.
Peter J (at least I think it's Peter's) has a method where he builds the MDF cabinet, then cuts out 3/8" x 3/8" pieces from all edges and inlays solid pieces of the same wood as the veneer. These pieces are flush trimmed then the veneer is applied to straight sides. Once the veneer has dried, the roundovers are applied utilizing climb cutting (and very light passes). This cuts through the veneer and the roundovers end up in the hardwood pieces that were inlaid. You can see a picture of an N3S done with this method here ( http://gr-research.com/n3-1.aspx
). Scroll down towards the bottom of the page.