Hi

I want to add a second graphic card to my pc to mine ethereum.
I have already a pc with Gtx 1060 6gb sc that i use for mining and i want to add another gtx 1060 6gb.

So my question is about my psu, i have a Aero cool 650wat, how do i calculate how many graphic card i can use depending on my power.

My second question is about graphic card choise, is it ok to use another range like gtx 1070 ti ?
If so should one miner per graphic card or one to handle them  both ?

I use PhoenixMiner and Gminer (i alternate to test them xD)

Thank you in advance for your time to respond me.