I'm building an amp right now. When it's done I plan to send the aluminum case to an instrument maker friend of mine to wrap it with a wooden case. You seem to like the wooden one. Find somebody who's good at woodworking who can simply replace the enclosure with something aesthetic and natural. Or PM me and I'll refer you to my luthier guy in Michigan. Getting one made in metal would probably be pretty costly, and given the shape I can't imagine you can find something off the shelf.
The Headamp front and back look okay but for the writing on the front. You could replace the knobs with wooden ones -- burl, maple? -- or silver or gold colored..
I agree with the poster above who questions putting a lot of time and money into a low-end amplifier. But if it amuses you, hey, it's your amp. And I can't think of any mid- to high-end 4-channel amps. Not that I've researched it.
Some custom box makers:
http://naturalrenaissance.web.officelive.com/CustomOrders.aspx
http://www.etsy.com/shop/JMCraftworks
http://www.facebook.com/krtwood