ITunes media on a NAS, libraries locally?

Question

Hello, all,
I've been browsing search results on hosting iTunes on a NAS, and I had a couple of questions and perhaps someone has some wisdom to share.
My girlfriend and I have separate iTunes libraries that we would like to combine. We are each on an iMac: hers is running Snow Leopard, mine is running Lion; each of our computers is authorized to play each others' music as far as older FairPlay DRM goes. She and her kids sync their iPods on her machine; they each have intricate playlist structures that I think have evolved into sentient life forms. I sync mine on my machine. We each have our own iTunes/iCloud accounts, and each have our own sets of iPhone apps.
We are attempting to migrate her user account over to my iMac, as a way of load-balancing the available computer time, as it were. So now the question is how to keep all the media updated between the two machines; it would appear that the best way to do this would be to merge the two libraries. I currently keep my iTunes and iPhoto libraries on an (old, and getting older) external firewire (400) hard disk. We both need to update our storage, and so I'm considering two different approaches:
(1) NAS. Have a partition for Time Machine, a partition for a combined iTunes library, and a partition for file sharing.
(2) New, larger Firewire 800 hard drive, combine our libraries. This wouldn't be accessible, though, from both machines.
So some questions about option (1):
--I understand that if I copy the entire iTunes library and media to the NAS, that that can bring everything to a crawl. I currently have mine on my external drive, and all user accounts on my machine have access to it and use the same library. I get the feeling that if I utilize the same tactic here, that everything will operate very slowly.
I've read that if I copy just the iTunes media library to the NAS but keep the actual library files on each local machine (and, I guess, user account), that not only would that speed things up but would also enable each user to have their own library, with their own playlists and their own play counts etc. But how would that work if User 1 purchased a new song or app? Would that new media only be added to User 1's library? Or would it become available to every library (I would prefer the latter)? How can this be made to happen?
--Songs are easy enough, but what about apps? If an app is purchased by User 1, using Account 1, and iPhone 1 is linked to Account 1...that part's easy. But what about User 2? Does User 2, using Account 2 on iPhone 2 also have access to that app? I'm not interested so that I can avoid paying twice, that's not the issue: but if all the apps are stored on the same library but are purchased from two different sources, then how would we/should we keep them separate as far as syncing with our iPhones?
And a question about option (2):
--So let's say I just bring my girlfriend over to my iMac, and do something similar to what I have now: a shared iTunes library on a new external drive, with all users on my machine using the same library. Her user account still is tied to her iTunes account while my user account is tied to my iTunes account: each of us can purchase music, and each piece of purchased music drops into the exact same library. How, then, to keep that library in sync with the library on the other machine?
Here is my idea, and would like feedback: if she makes all her purchases (songs and apps both) on her machine rather than on  mine, then using iCloud should not all those purchases (again, songs and apps both) also download to my machine as well?
Thanks for any help you can give!

Answer 1

HI
Read this user tip Make and keep a backup of your iTunes library, and only stream from the cloud.
Problems? No hidden catches. Whilst streaming using match, you will need a wifi connection. You main worry is that if your NAS drives fails, you need to redownload your music from match but this could take time depending on how large your collection is. Personally I keep an additional backup of all my music as a matter of course.
Jim