Airport Express Doubts

Hi,

Basically I am looking for wireless/bluetooth receiver for digital output. I have Yamaha receiver - basic model RXV373 which doesn't have network/bluetooth.

Mostly I will be listening music from my Windows PC / Mobile (iPhone/Samsung). Connecting mobile and PC everytime to the AVR is hectic and want to play it wirelessly.

I have tried apps like iMediaShare, Twonky Beam, Ace music...the issue with this app, we cant play the playlist as we want and also playing music from spotify or other online streaming is hectic.

I have thought of buying Airport Express..but having below doubts

1. Will it support both iPhone / Samsung...my wife is having samsung and I am with iPhone..Also can I play music from Windows PC...If we are going for bluetooth receiver, definitely it will support all bluetooth devices...

2. My wifi router is in living room, I want this receiver in my another room where my AVR / PC is setup. Do we need to connect ethernet cable from modem to Airport to listen to music?

Meaning i have a wifi network with a router from the cable provider
i have an extra airport express (not connected to the wifi network) that i would like to use just to stream music from a receiver using airplay without connecting to the existing wifi.

This way, i can play music remotely from my iphone without phyically connecting to the receiver.

Is this possible?

Ok below is the existing setup.

EXISTING SETUP
Cable modem connected to wifi router in the living room.
My laptop(windows), iPhone 4S, iPad, samsung galaxy s3 and Yamaha RXV373 AVR in the bed room.
All my above devices are in my existing wifi, except my Yamaha RXV373 AVR.

SETUP WHICH IAM EXPECTING:
Buy airport express.
Configure it to solely to use Airplay.
Meaning, my music in iPhone, windows pc, iPad and Samsung galaxy to stream my music to airport express which in turn connects to my Yamaha AVR.

NOTE: I CANNOT have the Ethernet cable running all over my living room to bed room to connect it to Airport express.

Main purpose to listen to music/streaming from third party like spotify/exfm to YAMAHA AVR wirelessly.

Also the airplay icon will be displayed / supported in all the iOS app like spotify/exfm?
From Windows, can I airplay from iTunes only? FOr Example, is it possible from Windows Media / VLC / Winamp?

I can achieve the above with Bluetooth which will connect all the devices which will have Bluetooth icon to play with. Bluetooth range is also not a problem as I am going to use it in my bed room.

Only concern in using Bluetooth is sound quality.. If we are buying BELKIN HD MUSIC RECEIVER which is sporting digital coaxial and digital optical output,,..but anyway using A2DP codec and not APTX codec which costs around $100 SGD.

For this, i can spend additional 28$ SGD for Airport express ($128) which will have better sound quality over wifi....and also be used for Internet/connecting printer in future.... BUT IT SHOULD MEET MY REQUIREMENT OF STREAMING MUSIC TO MY AVR (from app like youtube, spotify, itunes, exfm, etc...) ELSE IT WILL BE TOTAL WASTE FOR MY NEED.

Any suggesions