my router & airtunes separated

Simple answer: nope.
Just join the Airport Express to your existing wireless network. Sorted.

 

There are several ways that you can establish separate network segments but you would to provide more information about how the network is setup, what devices you have, and how you are using it.

There is no need to do this though. I'm not sure why you want to.

I currently have a network using both N and G. Much of my gear is hanging off an N Airport Extreme which is serving DHCP. That device is connected to my DSL. This Extreme is serving N only and used as a bridge to an Extreme on the other end attached to my home theater (HD Slingbox, HD TiVo, and my Blu-ray and HD DVD). It also serves my MacBook Pro.

One of the ethernet ports on my primary Extreme is attached to an older G Airport Extreme. This device serves as a host to a G-only network segment that also receives its DHCP from the N-only Extreme. This unit is the main device in a WDS, with each node in the WDS configured to also host wireless clients. This network is stuff that either doesn't need to be fast, or is old. The nodes are 2 older G Airport Extremes (spaced far apart) and 2 older G Airport Expresses (for streaming iTunes to 2 locations). The various wireless devices hosted are my video game consoles, my iPhone, and my old PowerBook.

The bottom line is that these networks can be really flexible, it's all just about the money.

 

Yes, just set up the express to join your existing network, doesn't matter that it's not an apple base.
You will probably have to plug the express in with an ethernet cable (either to your existing network, or directly into a computer) to set the express up.
You can set it up, and then unplug and move it to the final location if that works better for you.

and yes you are correct, you don't need to bother with WDS.

 

I was going to ask something along the same lines...

I want to have wireless iTunes, but I use my Airport Extreme already for a Hard Drive and printing... So I assume I can't do all the functions as one??? (The hard drive acts as my media storage... so if I wanted to listen to music on the wireless speakers with the airtunes, I couldn't?)


Also, does having 2 wireless routers in 1 room mess up the connection?

 

wayland1985 -
you can connect to both an extreme and an express at the same time. so your situation would work.

if the routers are both in the same room, you don't need to have them both broadcasting,

either
set up the express to join the wireless created by the extreme,
or
just run an ethernet cable between the 2, and turn off the wireless on the express.