Want to upgrade my computer for this game, need some advice.

[Niqote]

What's your budget? If you can swing it, I highly recommend looking into Nvidia's 900 series. Probably the best cards on the market for various reasons.

The thing is, I need two :3, my SO could use the upgrade too.
Like this? Are they all one size fits all?
I'd hate to buy something only to find it wont fit where my old card went. But they are the same brand so it should be ok right?
Does the power supply need any consideration when upgrading only a graphics card? I tried googling but I just gained more questions.

[Bourne_Endeavor]

The thing is, I need two :3, my SO could use the upgrade too.
Like this? Are they all one size fits all?
I'd hate to buy something only to find it wont fit where my old card went. But they are the same brand so it should be ok right?
Does the power supply need any consideration when upgrading only a graphics card? I tried googling but I just gained more questions.

Unfortunately, no. It isn't one size fits all. You'll need to determine what your case can handle, then pick a card based on that. And generally speaking, yes. But in this case, the 950 actually draws less power. It's also smaller. So if that's what you settle on, you'll be set.

What to do is build your PC on this site: http://pcpartpicker.com/

It lets you put together every piece you'd want, finds the best outlets to buy those parts in your Country and warns you if there's an issues about compatibility.