This is what I want to do... but I want to keep the AAC on the iMac and lossless on my external hard drive. Any suggestions?
I ripped my CDs as Apple Lossless, added all the album info/artwork to the tracks. Then I copied the album folder over to my external hard drive. Once the lossless version was on my external hard drive, I converted the songs in iTunes to AAC and deleted the lossless version.
Basically, my iTunes on my iMac contains only AAC versions of the songs and my external hard drive contains all the Apple Lossless versions.
The way I did it, I won't be listening to the lossless versions, just the AAC versions. I only ripped them that way so that if I ever wanted to go to a higher bit rate, I could without having to find the CD.
It would be nice if iTunes allowed multiple Libraries, almost how Mail allows multiple Inboxes. That way, I could view my AAC songs and my lossless songs separately and also have them stored in different locations.