I don't really see anything wrong with that Ebay kit, all you really need is a well shielded box with decent RCA connectors. The CM-1254 are shielded in MU metal cans so the metal box is mainly to shield the exposed wires inside.
You might want to contact the Ebay seller that sells the finished chassis for plug in style transformers. He uses the very nice Hammond die cast aluminum chassis. I'm thinking he can sell you a chassis with all the parts and predrilled to mount it all in. Be worth a shot.
BillWojo