Maintaining seperate iTunes libraries for portable and home use

I have a Buffalo NAS with a 2GB Hdd currently installed which I going to move my media to including my iTunes library. I would like to have it so that I have the master version of my iTunes library on the NAS (which will be backed up to an external 2GB USB HDD) that any of my three Windows machines (two laptops and 1 desktop) can access directly when on the network and on the two laptops a cutdown version of the iTunes library as well stored local on the laptop's HDD for any music and other media for when I am not home to able to access and to sync any changes to and from in the music part of the laptop's cutdown library (if I happen to purchase any music when I am away without having to sync via iPad/iPod) or add/remove any extra media to the cutdown version from the master library without deleting it from the master library on the NAS.