I have to admit that you didn't choose the easiest solution as :
1. The PS3 is not the best mp3 player on the market concerning ease of use...
2. You could have put a 1Tb hard drive directly INSIDE your PS3 and filled it with your music instead of searching complexity with a NAS (but as you also want to play video, I see the utility of a NAS)
3. You could have turned on/off the PS3 with a BT/IR converter instead of a USB stick. Now you can also turn it on via a Bravia TV, but that's another story...
4. As you have a Beo5, you should be able to make a macro which turns the TV ON, select the PS3 input, turns the screen off (picture mute) and select Speaker 2, everything with just one button... Two with the PS3 ON button!