Denon AVR1400h - add pre out

Hi,
I own a Denon AVR1400h Euro version. My release hasn't a pre out asd the US version. I think the mainboard is ready to add and I think it is possible to sniff the pre out signal before the power amp stage.

What do you think ?
 
I've the electrical scheme.
My mainboard has the correct lines for the zone 2 preout , in any case I need to have a pre out for the front loudspeakers.
I see that my amp lacks some transistors and capacitors . they are for a signal gain optimizer .