How can i add a stereo receiver and speakers to my setup?

What do you have in mind? salvage a pair of speakers and a stereo receiver to create a 5.1 setup together with your existing microlab active speakers? If that's the plan well I guess you will end up spending more money and eventually not enjoy the audio. Your speakers will not be compatible not to mention balance since the power requirements differs. Definitely you will need a digital multi-channel soundcard because a stereo receiver is good only to drive a pair of speakers. Another thing is how to do the connections. Maybe buy a cheap but decent media player and use it on your stereo instead. I've done the same thing before and I called it "chop suey" (mixed ingridients..)and so is the sound.