Best way to hook up Airport Express with a current Airport Extreme network

Question

I currently have an Airport Extreme (7.2 firmware, N version, but right now running mixed mode because all my clients are G, and using WPA/WPA2), and I am thinking about getting an Express to use it to share a printer and the Airtunes feature.
My Extreme is on the top floor of a 3 floor house, and has good coverage over all the house. So I don't necessarily need the Express to extend the range on the bottom, but if it helps get a stronger signal, then why not. My stereo and printer will be on the bottom floor as well.
There seems to be several ways to add the Express to the existing network, but I don't which one is the most appropriate or what will work the best.
1) Do I use a WDS network?
2) Do I extend the network?
3) Or setup up the Express as just a wireless client for Airtunes/printer sharing?
4) Can I put a USB hub on the Express and share a printer and a hard disk? (I would do this on my extreme base station, but its in a location that I can't attach it to a printer or hard disk)
Thanks for any help.

Answer 1

would this approach work if the extreme were in "n" mode and all you wanted to do was set up the express for air tunes? would "b" or "g" machines be able to "see" the air tunes "station?
Since the AX is an 802.11g device you would need to run the AEBS in an 802.11g compatible mode for the AX to wirelessly connect. Therefore your 802.11b/g clients could join the AEBS's wireless network. The AX service would be available to any device connected to the network.
if one had a dual band network (an extreme in "n" and an older snow base station for "b" and "g" connectivity), how would this affect the use of an express for air tunes?
In a dual-band network one of the base stations is acting as a bridge. Therefore every device connected is on the same subnet and able to use the services of the AX. This is regardless to which base station they are connected or if they are connected wirelessly or via Ethernet.