music, personally I use the google music beta so got the 4.01 apk (the leaked ICS one) and using that,
films, streaming is the future, set up a upnp/dlna server on the pc/nas (wmp just about does it on windows, mediatomb seems very nice for linux) then get bubbleupnp, mx player and/or mobo player for the touchpad as video players (those will obviously also work with video's on the device).
At the minute I have to use software decoding in both of those players, so it can handle normal vids but not so much the 'hd' ones (I generally get/use 720p mkv's ~1.6-2Gb per 45-50 minutes).