[ubuntu] Nvidia drivers and 16.04

I updated from 15.10 to 16.04.

Bad suprise when booting again, login screen is is poor resolution, and unity won't start.
After recovery mode and "apt-get purge nvidia" It switch to nouveau drivers, and it "work". But, steam needs proprietary drivers, and installing the nvidia drivers (361), get me back where I started.

Any ideas on how to fix this ?
Edit : i forgot, GPU is a Geforce 970