Surely that depends on if you got a sub that automaticly filters the low tones from the front & rears or not? My sub even works when the center/sub channel isn't plugged it, it works a lot less, but still takes the low tones sent to the other channels. That may be for all you guys that do have sound in those games. While the op migtht have a sub that only plays the stuff it gets on it's own channel/cable. and CSS etc might just not send stuff directly to the sub?
Just a theory though.
Oh, you can't compare 5.1 to 2.1 btw, 2.1 filters stuff from the left and rigth channel and plays it.
On 5.1 and 7.1 the sub has it's deticated channel directly plugged in with the pc, the pc can communicate directly with the sub.
Whereas in 2.1 the sub just searches the left and rigth channels, takes the low tones, and plays it. This also happens in some 5.1 speakers like mine, but all 5.1's sub's also have their own channel so they can be controlled directly from the sndcard/app.