I have been playing with my new setup and finally finding uses for multiple airplay speakers at one time. I see that I can stream to my gen1 airport express as well as my aTV2. So I had the stream going to my aTV2 and then I chose multiple speakers. The only thing listed was the computer and an additional aTV2 in the house, I did not find the express. Is this a normal function? Are there limits to the number of devices?