Usually on those type of monitors, it's just a simple amplifier circuit between the input and the speakers. Just pop the back off and have a look around.
Just remember, if you are going to use a VGA TV tuner, the sound comes on a separate line anyway, so you could always just use a set of amplified PC speakers or something for your sound. It would probably sound worlds better than the 1/2" squeakers that are probably in that monitor
