Option 1. Faster than the 780, but most importantly, it has 4 GB VRAM. 3 GB on the 780 may not be enough for 4K editing. The only drawback is that it does not support the obsolete Ray tracing in AE, but that is being phased out. Dual video cards are not an option with your CPU, so do not waste your time and money on those considerations.
I must have missed the memo with no Dual GPU not being an option with the CPU. I really prevaricate the quick reply. I guess the question now is because that is not an option do I just put the 980 Ti on the credit card, is the extra $$ really worth it though.
As I'm just doing casual editing at the moment, I could always go with the 980 and when/if our production company does start making us some money, I upgrade to a Titan.
On a side note, the Quadro Cards have also been suggested a few times.
Quadro's are overpriced and underperforming, as shown in the link I gave earlier.
Even if you over clock the 5820 to around 4.5 GHz, you have difficulty in using all the power of the 980. The 980Ti may, may give a tiny performance boost over the 980 in this system, but the extra cost makes it an unattractive alternative.
if you want to improve the system, invest in a couple of Samsung 850 Pro SSD's and a Samsung 950 Pro m.2 SSD if the mobo allows that for media cache.
once you get past the gtx 970, all of the other gtx cards are expensive. the gtx 980 ti is a fair amount faster than the 980, with about 40% more cuda cores and extra 2gb ram. that places the 980 (non-ti) in an odd place, its just priced too close to the ti version and should be skipped in favor of the 980 ti or 970. the 980 ti uses the same chip as the titan x, but has about 10% disabled cuda cores and half the memory. i would go with the gtx 980 ti for the extra memory and power to help with the red footage debayering. if you did need to add another gpu later, you could run two 980 ti's at 16x/8x or 8x/8x, leaving 4-12 lanes available for another pcie card/device. quadro's are built to be more reliable, but at nearly 10x the price for same performance, should be skipped for use with adobe apps, since they do not use the extra/advanced features of the quadro cards.
The 980Ti is definitely so close to the price range of the 980GTX there really is no need to consider the 980GTX if you want something better than the 970GTX card. I would always suggest the 980Ti or the Titan X card but the 980Ti is the best option for the price currently.