I did it! (rather bad solution)
Just have 3 ogg files for each sfx..
one center
one left
one right
Now....
1) Decide wich one to use based on your character X position
2.1) give a margin to the center value, do not use x1==x2)
3) Estimate the distance between you character and the sound, to set the volume.
Voila!
PS: This can be emulated in the Construct 2 export process