Like Jason said, that only has two inputs...
One for two channel(the red/white marked..."2ch: L/R"
And one for an ALREADY DECODED 5.1 (everything else above that 2 channel).
This is a basic speaker set usually bought for computer gaming.
You "could" purchase an old home theater pre-amp...but one...
The only review I found for Xenta(since you didn't provide a model number) is...
From Amazon.uk...
"The people who can't get all the speakers to work can't find the button to activate all the speakers."