Airport Express Airtunes

[reallyconfused]

After spending the good part of a day getting my AX up and working (as the sole router.. [cable modem -> AX -> wireless]), I'm having more troubles.

I got a good wireless signal and got it encrypted, however I can't get AirTunes to work (the whole reason I bought this thing).

I got my speakers wired correctly and when I open up iTunes, I see the AirTunes selection in the bottom right, however when I try and change to these speakers, nothing happens. I can only listen to music through the "My Computer" option.

Any help would be greatly appreciated.

Thanks.