Total itunes/airtunes setup from scratch, please.

I should add that the "several HDs where the music is stored" consists of two 1 tb drives, one of which is the main and the other a backup that I update manually. I would love for this to happen by itself as well.

I'm almost positive that AirPlay requires a computer running itunes or some other software (like Rogue Amoeba's airfoil) to serve the music out to more than one airplay device. You'll be able to serve media that lives on any of the iphones or ipads to one airplay device. I'm also almost positive that airplay devices will work with media stored on a NAS or airport extreme / time capsule, without a computer running iTunes accessing the media stored on the NAS / extreme / capsule acting as an intermediary. http://howto.cnet.com/8301-11310_39-20049405-285/apple-airplay-10-things-you-need-to-know/ has some additional information. It seems to confirm things. With iOS5, you can have all of your iPhones / iPads / etc sync over wifi with one computer. That has made things a lot better for me, as I've set up our iPhones to sync over wifi with my server, which is in my basement, and is left on all the time. It's not a Mac, but perhaps one day... The great things about Macs is their relatively low power consumption. Now, since you don't need to use the libraries on each computer to sync with your devices, you can just use the home sharing features to access the media stored on your central computer from your other computers, which negates the need for keeping multiple copies of your media around, or doing your USB drive dance. :) If you are keeping a computer running all the time (or at least when you want to listen to music), you can connect your two USB drives to it and set up an automated syncing / backup job to run daily or weekly or whatever. Alternatively, you could ditch the USB drives and upgrade to a NAS. So, you'd have one copy of your media on your computer and another on the NAS. Some NASes can backup to attached USB drives, so you can use that as a bonus backup. Plus, some NAS units, like Synology, can act as Time Machine hosts, which is nice. The benefit of a NAS over USB drives is that you can just pop new / replace drives in them to get more storage space. If budget is an issue, you don't have to fill the NAS completely with drives and just buy more as your budget and space needs allows. There are NAS drives that can take anywhere from 2 to something ridiculous like 10 or 15 drives. So most likely, you could find one to fit your budget. Now, whether you need an airplay device for each room will depend on your goals and a few other things: - are any of your rooms next to each other and do you want to listen to the same music in them without having to blast it in one room? - do you have any stereos or speakers in any of the rooms already? - how many rooms do you have, and where are they in relation to each other? - do you want to be able to listen to different music in different rooms? - do you want to watch your itunes content on your TV? If so, get an apple TV, which can also act as an airplay device. They make some battery powered portable airplay speakers. So, if you wanted, you could just get one of those and carry it around your house as you move around. You can see a list (probably not all available) on the http://store.apple.com/us/search?find=airplay+speakers. For any room that already has speakers or a stereo, buy an airport express. They are cheap and awesome, at $100. As a bonus, you can use them to extend your wireless network. Airplay works over regular wifi, so if you are happy with your wifi router, there's no reason to replace it.

This is not my area of expertise, but I am currently setting up a more modest system that does some of this. Take a look at the Synology home servers like the http://www.amazon.com/exec/obidos/ASIN/B0049MPQGI/metafilter-20/ref=nosim/ which takes 2 sata hard disks, plugs into your router with regular network cable (not usb), can be set up as RAID array to keep two identical copies of everything, and runs AirPlay. It also does a lot of other stuff. Doesn't draw much power, and goes to sleep when inactive. Manufacturer has a great reputation, and there's a fairly active forum community to help you figure out how to get set up.

I'm a big fan of the http://www.logitech.com/en-us/speakers-audio/wireless-music-systems line of products.

Seconding a NAS box from Synology. I have had a single-drive unit since 2007 and recently upgraded to a dual-drive box RAID-1 for drive failure protection. Specifically, the new box is the DS211j as linked by jon1270 above. Our TV has an Ethernet jack and it streams video, can play photo slideshows and music, directly from the NAS no computers involved. Check out the Synology website for additional features, they have a lot of them including iTunes features and iPhone integration and such. It's easy and it works and we love it.

The http://www.netgear.com/home/products/wirelessrouters/high-performance/WNDR3700.aspx WNDR3700 router has a built-in DLNA server and accepts a USB drive so it acts like a NAS and like a server. You can use http://xbmc.org/about/ to play music right off the drive or you can use the DLNA server to do that. However, you can start playing with XBMC to see what it will do for you without changing any of your hardware. It's free, and it's slick.

Hi Jon1270. I didn't know that Synology supports airplay. How do you enable that? Do you have to hook up speakers directly to it, or can you stream music off it to an airplay device?

reddot, I don't actually know that much about AirPlay yet but the current disk station management software includes an application called Audio Station, the description of which says "Enable Audio Station to play music through computers, USB/UPnP devices, iOS/Android mobile devices, or AirPlay devices." There's no way to hook speakers directly to the disk station (except maybe via USB? I don't know if that's supported...), but I would assume it can talk to AirPlay devices using your household wireless router. When I want to play music through my home stereo, I'll probably just use an adapter cable to attach my iPod touch to the stereo's aux input and stream that way, rather than buying a dedicated device.

I can't answer your question, so feel free to take this with a grain of salt, but... If you are starting from scratch, would you please consider switching from iTunes to http://www.jriver.com/index.html? It is a much much better way to deal with a large number of files/devices. I cannot stress enough how much I love this software. I have been using it for 8 or 9 years, and they have never stopped updating and improving things (and, no, I do not work for them, promise.) It includes several http://wiki.jriver.com/index.php/Servers, so you can do things like access your home library from anywhere on the internet or another machine running the same software (anywhere, not just on your home network), and use your iphone as a remote. There is a lot more info on this in there (incredibly useful and constantly updated) support http://yabb.jriver.com/interact/index.php, http://yabb.jriver.com/interact/index.php?board=7.0 is the media network specific one, which you might want to have a look at for ideas. I have just barely gotten started on their media server stuff, which is why I answer your question, but if you're interested those links should get your started. Even without that stuff it is still a far superior system for organizing your music (and videos, and images), so I hope you'll consider it. Sorry about the fanaticism, my music setup is really important to me.