Stream music trough AirPort Express connected only to my stereo

I want to wirelessy stream the music I store in my Synology NAS to my old stereo. Doubt if AirPort Express can fulfill my needs considering that:

AirPort will be not directly connected to my wifi router, but only to my stereo. Referring to

http://support.apple.com/kb/HT4587?viewlocale=en_US

Connecting to an existing Wi-Fi network, exclusively for iTunes music

AirPort Express need a AirPort wireless LAN already in place to work? The only wireless LAN in my home its the standard WIFI network and the wifi router its not Apple. My NAS is connected to this wifi router.

This thread describe my concern

https://discussions.apple.com/thread/2715375

I just don't understand if this is a working solution, but my situation its the same: I can't connect AirPort Express station to my wifi router since they will be in two different rooms, and I haven't any other AirPort station.

- Also the same page state "Do not connect AirPort Express to the phono jack on your stereo". Can use the AUX port of my stereo?