to ryantsui:

I can't find detail information for the product you buy in the internet. In general condition, there are only two analog stereo headphone adapter on you LIVE! soundblaster card, one is for the front L/R speaker and the other is for the rear L/R speaker. Under this configuration, there is not standard analog output adpater for Dobly Digital (AC-3) for your sound card.
You have two option to get the surround sound effect.
First, you can connect the S/PDIF output from the sound card to an extra AC-3 decoder like general AV amplifier.
Second, just like what you did, buy two set of speakers and a subwoofer. By this configuration you can get a AC3-similar surrond sound effect by a cheaper price. For this second option, there is a lot of selections of speaker sets. Some have an internal AC3 decoder and the others doesn't. According to what you said, I guess your Microlab M-800 should be one of the speaker sets that desn't have an internal AC3 decoder. In general condition, this type of speaker set you just connect the front speaker to subwoofer and then connect subwoofer to the front adapter of sound card, and connect your rear speaker directly to your rear adapter of sound card. The subwoofer will work automatically according to the singal that should be display by front speaker.
If you still have trouble with setting up your speaker with your sound card. Please reply and tell me more about the detail of your speaker set.