Wife read this post as she wants to stream movies from our PC or Lap Top (wireless) to our 55" TV and use the Yamaha RX-V1900 HD AVR for audio(listen to our HT speakers) movies from Itunes I loaded for my Ipod. Sorry to go off topic.... you got me to thinking

what will this cost me? I just looked Yamaha does not have any updates for the 1900... it's Big Brother the 3900 does.
Based off my understanding of what you are wanting to do, I'd probably recommend something like the
Boxee Box. While there are cheaper alternative solutions out there, I would say none quite meet the elegance/ease of use of the Boxee (VERY high WAF). You could also make use of a PS3 or Xbox 360 if you have one attached to the TV using a media server (TVersity, PS3Mediaserver etc) as matty76 suggested, but it doesn't look like you have one based on your sig.
Edit: Actually I re-read your post and see you specifically want to use iTunes. In that case, I'd simply get an AppleTV for $99 and use the Airplay streaming function. It is much less versatile than the Boxee, but has it's place if you are fully invested into the iTunes ecosystem.