thanks for the replies.
i thought about using fm transmitter with old radios would be an idea too, if something wireless is needed. i like the idea.
if i dont use the connected version, the playing should be in random mode. maybe cheap active speakers and used minidiscplayers with random mode are a way to do it.
i also thought about building my own sample and hold units. maybe there are some nice circles in the web.
when i calculate all the possibilites named before, i get the result that a good audio device is cheaper and gives me more possibilities. anyhow i like the other ways. i found the esi gigaport hd for around 150 €. this is a good price for 8 output channels. but i think it wont run under linux. but this is another problem. its much cheaper like the firepod. for the beginning this seems enough.
the relay idea is a nice one too, i dont need sound on every channel the same time, but it would be nice. but i think the technical realization is many work.
what do you think,which is the easiest way to amplify the single signals. what amplifier method do this little active speaker for pc use? i think this would be enough power for high frequencies. for the deeper i will take old carhifi equipment i think.