I just went through your current situation.
I have a laptop with the iTunes, wireless to router(Netgear N300) and the AVR and bluray player for TV ehternetted to the Netgear n300.
I got a wireless router with ethernet ports so it is a combo wireless and ethernet setup. Search Netgear N300 wireless router. Wireles(which means u run a cable from the modem(your cable connection) to the router.
Internet access comes in direct from the wall to the black box in my case) via ethernet to the wireless router. From the router u will notice it has 4 ports to use. That means u can connect 3 other devices and the AVR and any wireless gizmo u might have. (laptop for instance.)
I actually got an Airport Express($99) and saw it wasn't going to work for my purposes. Look online at pics of the Netgear n300($59Radioshack) and the AE. I think u can see good clear pics of the ports and connections. I even called Apple for the sale and ask a ton of question but i just sent it back no questions asked..
Anyway, I have a very hard time visualizing what I need when it comes to wiring this stuff,but then it seems so simple, if that is any encouragement.
I thought i wanted wireless for Airplay but downloaded a bunch of stuff from the iStore and a few did not download properly. So, I am going with the ethernet, better connection, better privacy.
I am no expert so if what i have said isn't right someone please chime in, I'm just trying to pay it forward with all the help I received at AVS.