Prodigy^, if i am not mistakened, the soundcards (esp. the newer ones) aren't exactly the juice suppliers but rather are built to give out a better 'quality (and low noise) juice'. in an ideal case, you might want to connect the output from the sb live to a stereo system/home theater system and let it amplify the sound. this is what i do. in fact, that gives you one more level of sound tweaking possibility with the additional stereo/home theater sys. controls.
to support my statement in a better way, the good, consider how the high quality speakers (take Terp's Cambridge Soundworks for example) require and come with an power supply. where do you think they generate the high watts and powered ouput? definately not from the juice comin out of the sound card! the power is needed to amplify the 'small amount of good quality juice' tricklin out of the sb live cards which then gets amplified by the speakers.
correct me if i am wrong but i pretty sure this is exactly how things work out.