Can I get away with replacing just my Graphics card?

[Boomasures Rex]

I would like to build/upgrade (I understand they're two completely different things but ill get on that later) to run gaming with friends online better, as well as support VR gaming. Im looking to spend about $1500 but the more I can save the better.
My current build is Intel Core i5-3450 @ 3.10Ghz Asus P8H77-M PRO/CM6870 Motherboard EVGA GTX 660FTW 2GB 12GB DDR3 Corsair 550W
Now my questions are; 1: Is my mother board good enough if i wanted to get a EVGA GTx 1070 Super Clocked 8GB Or should I upgrade if so to what? 2: Should I just sell what I can from current build or should i keep hopefully my Power supply, Ram, And hard-drives and upgrade processor, motherboard or graphics card. 3: Should I upgrade my processor? If so would a Core i5-6600k be good enough and worth it?
Your going to be helping a novice when it comes to building a PC, If anyone would personally like to help me on what i should do youd be amazing. Thank yall so much. Game on.
(P.S. I apologize for anything i got wrong, tech wise as well as grammar.)

After posting this on Reddit some friends informed me that the only thing I NEED to replace is my graphics card, is that true? Would replacing just the be a valid option for me to run games better and VR? Thank yall so much.

 

[khachira]

EVGA 1070 superclocked is good enough for VR, but you need to change that CPU tho

edit: also retain that power supply, and whats the RAM speed? since it's DDR3 i'm a little bit concerned.