the connections your doing may be correct, it may be your sound source. I remember reading somewhere (prob on these forums) that its all to do with the sound source. If you try playing a dvd it may come out of all 4, but if you try playing just a mp3 then it just comes out of the front. Its to do with the type of encoding. I may be talking lots of bolloxs, but I did read it somewhere honest.. :-) maybe someone can explain it better. (fingers x'd)
you won't get the rears to fire on something like an mp3 without turning on stereo expansion. On my game theater there is an option in it's setup appliction. I'd susspect there is something simmular on the epia but I've never tried to get 5.1 out of my epia.
I have the same problem, and I'm pretty sure the other channels are not active on mp3 playback. All I did was flick the switch on my amp to 2CH which activated all 4 speakers on 2 channel sound.
2.5" Hard Drive 80GB Samsung 5400RPM
256 MB DDR2 PC5400
Xenarc 700TSV - VGA Monitor
Intel D945GCLF Motherboard
2005 Honda Civic