yeah you could do that
or at least look to see if you can use the internal amp
6ohms is ok - but 16 ohms is too much
most computer speakers are 4 ohm and also have a low-pass cap installed somewhere so that the speakers dont blow on low low bass (normaly 50hz and lower) depending on the speaker
cheap speakers have cheap amps 1-5 watt wich is not much
i've hacked computer speakers for the amp in the past - pretty easy and effective
http://www.liquidskymusic.com/quiet/-projects-/speaker/is one project
enjoy