iTunes Library Management (and Heirarchical Storage)

Dear Lazyweb….
I have a huge iTunes music library (about 65GB worth). Right now, that all sits on my laptop, gets backed up when I back up my library, etc., etc. At any given time, I’m really probably only “immediately interested” in, maybe, 10% of that.
I’ve got a NAS in my basement. In my perfect world, there would be some software I could run which would keep my NAS as my “main repository” but give me the option of dragging stuff from my NAS into my “currently deployed” iTunes library. This would free up space on my laptop, make my backups faster, and just be overall easier to deal with.
If I had a “spare” Mac running, with space available, I could use SuperSync to shuffle tunes (and their meta-data) between the two systems, but I don’t see any easy way to do that just with some spare NAS-space.
Anyone done this before and have some pointers?