I just bought a Trust 5.1 Surround Sound Card SC-5250 (a cheapo sound card i know) which i'm having problems with. I'm running windows XP SP2

I have a 5.1 speaker system (5 speakers + bass) connected to an amp which in turn is connected to the sound card via 3 x 3.5mm stereo jacks (front L+R. rear L+R & bass+center).Using either winDVD or PowerDVD i get the same problem. If i try to play a DVD with a 5.1 (or more) audio track, and select in either players audio settings as 5.1 audio i get all 5 speakers+bass working but the centre speaker which most of the speech goes through is really quiet, even when turned up to full volume to the point that if you put all the speakers at full volume you cant hear the speech over the music and effects and even then all the sound if fairly quiet. If i switch either DVD player down to 4.1 audio, this fixes the problem, all the audio is much louder and the speech is mixed between the front L+R but the centre speaker is off. but strangly the bass which is from the same socket as the centre speaker works fine, just the centre speaker thats off?

Ive tried all the obvious things like swapping them round with other speakers to make sure its not the speaker itself, ive downloaded the latest software version for the manufacturers website, ive been through all the volume settings on both the amp, players and soundcard software to check nothing is turned down. ive used the soundcard software to dip the sound in each speaker in turn to make sure they're all connected up correctly, also been into control panel>sound & audio devices and tried all the speaker configuration options.

Ive emailed trust product support, but just wondering if anyone else had had the same issues before?