Arduino running multiple speaker setup

[system]

This is what I'm trying to do.
I need to play a specific audio file to a specific speaker (8 sounds and speakers total).
Each sound/speaker is played one at a time.
The setup will be in a larger room, but the speakers will be hidden inside objects.
I've attached a simple diagram of what I was thinking.

Using just an arduino and mp3 shield to output the audio (powered by a 12V wall wart -- not sure the amp needed).
Send the audio to an audio amplified (http://www.sparkfun.com/products/9612)
The 8 speakers connect to the amplifier through a set of 8 relays (and an 8 bit shift register), the relay picks which speaker is used at that time.
http://www.amazon.com/SainSmart-8-Channel-Duemilanove-MEGA2560-MEGA1280/dp/B006J4G45G/ref=pd_sim_t_4

I also am not sure what speaker I can use.
http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-090-6501M01-/52-185
Would these speakers work? Are these strong enough? Or need too much power?

Is using an amplifier overkill?

[andreena]

Hi Cyancdesign,
I'm also interested in something similar. Did you find any solution about connecting multiple speakers on different channels in Arduino?

So far I was advised to use multiple channel sound card, but it's too expensive for my project.

Please reply if you have any solution.
Best,
Elena