New to CNC, but found a place to make a contribution!
You can buy individual wood pieces on ebay, such as
http://cgi.ebay.com/Walnut-spalted-F...QQcmdZViewItem
As the above board is only 7", it would need to be bookmatched to look good when joined to make it wider. The reference board previously posted looked to be a single piece of wood, and is likely an exotic.
Poplar is not intended for finish work. It is great for painting and veneering. You see poplar used on good quality furniture to make the carcass and drawer sides, as it is strong, easily machined, stable, and relatively inexpensive.
My thoughts...
Dude, the CNC machine can be used to do a compbination of marquetry and ingraving. See
http://en.wikipedia.org/wiki/Marquetry . So I was thinking that the main board would be an exotic, with a nice middle carving as shown. The states would be in marquetry, using maple veneer, dyed with aniline dyes to match the color, see
http://www.raybernco.com/ex-tb.html
my two cents worth
John