Dmitry Sandalov posted a great in-depth article about streaming audio from Ubuntu Linux to a DLNA player without using Rygel. You can read the entire article here. I've tested his solution with my Onkyo receiver and it works fine. The idea is quite clever and simple: "The way I have it now: I pass the pulseaudio stream over HTTP, setup a ‘Favourite’ link on Onkyo receiver then play it. It works a lot more stable without DLNA server".