Suppose I was to connect this soundcard http://www.m-audio.com/index.php?do=products.main&ID=41cf7347b20eff77b69588578a74aa58 to an amp and then to the speakers. Would I need a preamp to adjust the volume and send the signal to the amp, or would the soundcard act like a preamp and let me adjust the volume from there, in the mixer for it?

I can definately get a better power amp for the same price as an integrated amp, or an amp of equal quality for a lower price than an integrated amp, so this is a bit crucial here.

Thanks.