The big issue you're going to find with DAC kits is that the parts needed to construct a DAC these days tend to be surface mount, and assembly is pretty difficult. So you'd need to look for a kit built with really old parts, which you probably don't want, or a kit where the surface mount stuff is already installed. That alone is a pretty tough request, and when you throw the tube output stage in the mix, there just isn't going to be anything left!