Sox is a sample rate conversion algorithm right? So it *should* work with this setup *if* you are changing sample rates via the DLNA DSP Studio, using Output Format. ...and if you have the Sox option checked in the main audio options.
But Jim said above that DSP via DNLA may not work. I don't use DLNA (much) and can't really test that. Perhaps someone else that uses DLNA a lot can confirm whether or not sample rate conversion works with this combination.
Brian.