Well, for a while I had struggled with a 4.1 card in my system, and not investing in a 4.1 speaker either. I have a Creative Sound Blaster Live! Value card. It supports 64 hardware sounds, and has a wonderful facility even supporting digital out. The sound is just peachy. I love it. =) However, my speakers are a different story. I have invested in a Mercury SW 980 2.1 system. It has a wonderful sound quality, but still sometimes you fell that a Creative Inspire would have fared better ;-). Anyway, these become my front speakers, the rear speakers (around 5 o them) are provided by my home theatre system (Aiwa).
So, since mom is off to Chennai, I was thinking of probably placing them in a proper surround setting so that I can get more realistic surround effect from my system and thought I'd do a simple googling on the right placement strategy. The results were mind-boggling. I am providing 3 links that go to the extent of providing the mathematics of proper placement =).  GRC Audio  Immedia Sound guide  Cox.net
Check them out. You will be baffled at the mere numbers that they are crunching and coming up with a placement strategy. But, they say that the best way is try out all the possible strategies and then use the best solution possible.
Gonna get my hands dirty and try out the various placement strategies mentioned here. Have to dig up that house plan, that I saw somewhere and start.