I recently added an Airport Express Base Station to my wireless network at home, with the primary aim of streaming music to the Hi-Fi in the kitchen, but I experienced mixed results.
My set-up comprises the following: Mac Mini and a Linksys WRT54GC
The initial set-up was complicated by the inclusion of an install cd and instruction booklet which as it turned out was only required by windows users. Instead of reading the instructions (as I did), all I needed to do was plug it in and activate multiple speakers in iTunes! Once this step was completed the Mac took over and automatically set-up AirTunes. I was able to hear immediate results and I was impressed by the sound quality.
However, music playback would stutter repeatedly to the point that I was beginning to think I had made a mistake in purchasing the router. I resorted to google. A quick search posed more questions and quickly pointed me to advanced settings in the airport utility where I was able to manually configure the router.
While the problem eased it wasn't resolved, further investigation returned many users complaining about something called IPV6. This post: solved all of my problems using the following steps.
1. Open System Preferences
2. Open Network pane
3. Select Airport in the left list
4. Click the Advanced button
5. Go to the TCP/IP tab
6. Set the "Configure IPv6" field to Off.
7. Click "OK"
8. Click "Apply"
9. Let iTunes connect to you're Airtunes speakers
During the process of trial and error I came across a wifi utility called inSSider. This programme (windows only) scans your locality for other wifi users and provides detailed information like which channel they are using and if it's likely they are causing interference on your network. I found another network using the same channel as me (6) so I therefore switched channels (11).
AirTunes is now working flawlessly and I am able to listen to my iTunes library throughout my house.