Surround Sound / 5 speaker systems w/ decoder

Hi there, I have the creative labs DTT2500 & 3500 speaker systems (one for home, one for school), both of which feature a DD 5.1 decoder control unit, 5 speakers, 1 subwoofer. I pass my audio to these speakers either via SPDIF or using analogue means. My sound card passes no discrete info to the center channel. Only stereo front, and stereo rear. Center channel info is normally derived via a function switch on the decoder unit, called "creative multi-speaker surround." I assume it enables the DSP which guesses at what sounds good for the center channel, derived from the other 4 channels. Ostensibly, the center channel gets real, discrete information only when the decoder unit is receiving AC3 information. What I'm wondering is if I encode my movies using 2-channel Surround or 2-channel Surround 2, and encode to ogg vorbis, and play these back on PCs, will my decoder unit recognize the input its receiving as anything special and decode it to the right speakers, or will it think it's just getting simple stereo input, and do nothing special with it? If it's not doing anything special with it, then why does everyone bother using Surround or Surround2, if the subtly hinted false-channels in it fall upon deaf ears?

Do a search on surround2 or dpl2. Or just look a few lines below your post, where this question is tackled. I also think that creative does almost the same as dolby, but doesn't call it dolby for license reasons. In the manual for my card it even says that I should use creative surround if I am hooked up to a dpl amp...

This question is sligthly off-topic from that thread, and is certainly not tackled successfully in that thread! But thanks for the link, it was an interesting (brisk) read.

This question is extremely important and I hope someone with knowledge can address it. Thank you.

Same problem I think