Did you want to carve these boxes out of solid aluminum billet? If price was no object, I suppose you could do it that way, but it seems uneconomical, both of time and money. Is there something special about these boxes that isn't available in the die-cast boxes you can buy off the shelf? (just an example: Die Cast Aluminum Enclosure - Econobox | BudInd )
Usually, people use their CNC machines to modify enclosures like this; putting in shaped holes and ports that hold components. But I can't think of any kits I'd recommend for cutting aluminum; mostly what you find in kit form is too light-duty for that.