making your own 4.2 setup

[couvier]

Im kinda a noob when it comes to this, but would it be possible to hook up two 2.1 speaker systems to a SB Audigy ZS 2 sound card to make a 4.2 system? Is this possible? So this would make it so you'd have 2 front and 2 back speakers along with 2 sub woofers. Can this acutally be done? I also assume that in order for this to sound good, you'd have to have 2 of the exact same speaker systems, is this right?

Also, say you have two 2.1 speakers, would there be any possible way to make a 5.2 system some how to get the front middle channel? Thanks for any info.