That's not possible - the warranty on the 990 (according to the user manual that I just double-checked) is five years, and the 990 has only been in production for just over two and a half years. Have you talked to Outlaw support about what you are encountering?
The only digital connections which are approved to carry a DSD signal are IEEE-1394 (firewire, which never caught on in the industry) and HDMI v1.2.
If you are talking about buying DVD-Audio software, you are a few years too late. There was never a huge catalog available, but I haven't heard of a new DVD-Audio release in almost three years. There have been some titles mis-identified as such (Rush has a DVD version of their latest album that was briefly publicized as being DVD-A, but it was actually just a DVD with PCM stereo and DD 5.1 tracks), and some early dual disc releases used DVD-Audio for one side (although that didn't last long).