I want to do the exact same thing as you. I want to be able to keep my collection on the computer as (Apple) lossless, and somehow sync a compressed version onto my iPod. This will allow me to Airport the (uncompressed) music to my receiver from my computer, yet still be able to fit my whole collection in my (40G) iPod.
Unfortunately, I don't think there's a way to do it without maintaining two separate libraries. I don't want to do this because I've already changed titles, composers, artwork, etc. to perfection. Just can't consider keeping two versions up to date. Hopefully Apple will make an update, but maybe not, since it's sort of a niche capability for audiophiles.
FYI, my encoded files with 128k AAC sound great through my iPod and Ety ER4P earspeakers. I experimented with higher bitrates, and couldn't hear a difference (not one I could identify consistently). I think 128 AAC is similar to if not better than 192 mp3, but of course this depends on many variables, including which encoder is being used.
Unfortunately, I don't think there's a way to do it without maintaining two separate libraries. I don't want to do this because I've already changed titles, composers, artwork, etc. to perfection. Just can't consider keeping two versions up to date. Hopefully Apple will make an update, but maybe not, since it's sort of a niche capability for audiophiles.
FYI, my encoded files with 128k AAC sound great through my iPod and Ety ER4P earspeakers. I experimented with higher bitrates, and couldn't hear a difference (not one I could identify consistently). I think 128 AAC is similar to if not better than 192 mp3, but of course this depends on many variables, including which encoder is being used.