Your audio output on the laptop may not have enough pre-amp voltage to drive your system to "shaking the walls" levels that you want. That could be either your laptop's sound card or your music was not created/recorded at the proper level.
As for not touching the laptop during your music and picture viewing, how will you control it? Wireless mouse? Remote control? One of those nifty gyro-mouse/presentation things?
Why not use a dedicated network device to do this? There are dozens on the market that do music, music/pictures and music/pictures/movies. The big network players like D-Link and Netgear have them as well as the smaller players like Buffalo, etc. There are companies dedicated to these devices like Popcorn Hour Media Tank. And then there are a bunch of
un-tried devices that start around $50. Even
some DVD players do this. Just plug a USB drive into the port on the player and you are all set.
Finally, what format is your music stored in? Wave? Lossless AAC, WMA, Og, FLAC? A lossy compression format? If so, what bit rate? What kind of system are you using for playback?
-Robert