Im currently running debian jessie on a usb key.I had some hard time configuring two monitors (one dvi, one vga) with Xorg configuration by removing the Nouveau Driver, and installing Nvidia.Console mode btw has recognized my two screens but it's so hard to make them both work in gdm... Installing specific nvidia driver i got a blinking cursor on one screen, and the gdm on the other. But i could never have gdm on both... With nouveau one screen is black (no detection).The question is, could it be possible to keep the Nouveau Driver and the specific Nvidia driver(without blacklisting nouveau)? Because when i switch my usb key to another computer the Xorg crashes, whereas with the nouveau driver installed, it seems to work with different computers.Is it either Nvidia or Nouveau?Also, where are the nouveau driver settings when in all recent debian installations you have no Xorg.conf and everytime i tried Xorg --configure, i got my gdm crashing and never starting again.Thank you for your help.. 
Two monitors on debian jessie (portable usb)
debian;usb;nvidia;nouveau