yeah, having an external networked drive is helpful for sure... I plan on storing all my movies and music (plus TM backups) on an external drive that stays on my desk. I dont need to have ALL my music/movies with me all the time, just the movies i havent seen, and theres the ipod for music.
As for docking station, maybe a 23" ACD and bluetooth mouse/keyboard can cover it... and cheaper than getting the iMac.
For example working with CS3 it gets frustrating having to configure the palletes, settings, etc on multiple computers. same for desktop image, itunes library, etc etc... (i know there's .mac syncing and actually use it with my computer at work)
Just my 2 cents... right now i prefer the convenience of ONE computer...
cheers