You can't do what you say you're going to do. Multiple cards only work like that in SLI, which is obviously incompatible. You could use the 960/1050 as a separate PhysX renderer but the performance difference will be so minimal and will probably actually hinder your performance that it's not really worth it. Either way, for practical uses you can't just set up the displays to one card and games on another, they kinda have to be under the same housing.
In terms of pure performance the 960 is probably better:
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1050-vs-Nvidia-GTX-960/3650vs3165 So you might want to roll with that. Trying to do what you're wanting to do is going to cause too many complications for it to be worth it.
EDIT...