Hi there,
 
First time replacing the psu and decided to get myself a new graphics card as well. The previous psu I had was a very low end and while I was doing research on my ax850, it was then when I first heard of 12V rail. I wanted to know how exactly the gtx 770 has to be connected to the psu, a single 12V rail from the psu to gpu or the 12V is just an additional thing and other connections are required. I would also appreciate if someone could briefly explain the purpose of that type of connection. Is it simple higher current and a way to ensure that the card always has sufficient amount of power to run or there is perhaps something more complex? 
 
P.S Is there a difference between 12V and 12V+?
 
Thanks in advance

Is this the only way that this gpu can be connected or there are other, perhaps better combinations? The card has two 8 pin connections on it, according to the 6 and 6+2 set-up, the remaining 2 pins would be left unused? What are they for then?