if you don't need a "full" kit, I have used the remote modules from dantimax.dk before and they are very high quality. The input 2 has full switching of balanced and SE inputs and outputs, and they have a balanced attenuator board as well. They also have linestage modules, or you could use the well regarded Aikido kit from tubecad.com...
I am not associated with any of these companies, but I have experience with their products and service both of which are top-notch.