If you are serious about editing then go with 32GB of ram and a GTX760 or above.
Also, I only see two drives and I am guessing one is an OS drive. You should try to get a separate source and target drive. Or a RAID array. If you are rendering to and from the same drive then you probably don't need much of a video card if you are looking at rendering HD since the drive will be the biggest bottleneck.
gtx 970 4gb should match your cpu nice. its just over $340-ish, and might seem alot but its very powerful. the cheaper alternative is the gtx 960 2gb at $210-ish. both of these are latest chip series from nvidia and requires less watts than previous generations and amd.
i would suggest you look at something a little higher quality for the power supply, or at least one rated for higher watts so it doesn't have to work so hard. if you look at corsair's lineup you can see the cx is one of their lower models. Corsair Power Supply Units