when you switch it to 4.1 you should get 5 channels of audio, one for each of the 4 surround speakers and one for bass. Your bass in a 4.1 setup may or may not be JUST bass, it may be a full range output. If this is the case, you can use a low-pass filter to pass just the bass to the amp (most amps have one built in). Otherwise, some sound cards offer the ability to mix any of the channels to the front. If yours offers this, you should be able to click a check box that will allow you to mix the center channel to the front channels, and your dialog will be louder.