I know I'm not the target for this, but I preferred the "A600" style case... That did exist? Right? My memory isn't what it used to be 
Someone mentioned the C64C. It was released in 1986 and 1987 depending on country. In some markets it pretty much remained until the demise of the C64, in others it was replaced by the C64G (back to breadbox case, but lighter colour and either the original colour keyboard or a C128 style light keyboard).
My preferred combination in terms of looks is a C64C with old style (1985 model, black/brown with dark grey function keys) keyboard - not sure if any models were ever sold like that though Commodore did seem to sell a variety of odd combinations to manage stock levels of the various parts, but I put my old 1985 model keyboard in my C64C...
In fact, an "A600" case with the guts of a MacMini would be pretty fun
I'm thinking a real A600 or A1200 case with a Replay board... The hassle will be the keyboard interface (maybe take the MCU from a A500 keyboard, and use a Keyrah or something combined with the daughterboard, so a remade one with a PC style keyboard would be a tolerable alternative... A500 style case would be too big for me, though.
