Using the Headphone jack on the I-Poo you could quite easily connect it to drive external speakers, (volume would depend on speaker sensitivity & impedance)....
Done correctly I can see few issues, done incorrectly I can see a toasted I-Poo, (not entirely a bad thing).....
You could fit a small amp in the glove box & use this to drive the speakers, again you simply use the output jack from the I-Poo as the input signal for the amp, (I use an MP3 player in this fashion to test car amplifiers)....
Have fun, but don't toast your I-Poo.....