A 960 is much better than a 750. Even a 950 is much better than a 750: http://amzn.to/2cRA4Ti
(I don’t think you can reach for a 1060 under $600, though, but you can try: http://amzn.to/2cRAWYd )
That being said, you can probably save some money on the motherboard: http://amzn.to/2cagsuZ
If at all possible, go for SSD instead of spinny disk. 512 GB SSD is much better than 1 TB spinny: http://amzn.to/2cztcNY
You should probably also save $20 on the CPU and get the 6500 if you’re not going for the 6600K: http://amzn.to/2cfEsiZ
Finally: You forgot a case and power supply in the cost 