Yes, i have seen ALSA website.
And yes, i have been playing with different mixers.
With surround, if i balance to rigth, it sounds in rear left, and the same if i balance to left, so my rear rigth speaker never sounds.
The other controls i think that works well.
And i dont know any program to try if 5.1 is working. In doom3, if i select this option in configuration, it says that there isnt surround system.
I dont know what can I do.