Ok now I have a few minutes. Watchdogs recommends for ultra at least a GTX 670/AMD 7970.
Source : http://www.vg247.com/2013/10/03/watch-dogs-pc-specs-revealed-in-full-get-the-list-here/
Source : http://www.gamersnexus.net/gg/1352-titanfall-pc-gpu-benchmark-full-version
This on a 3570k @ 4.4 GHZ so your CPU will be roughly equivalent. Looks like a GTX 760 is the minimum for Titanfall to avoid dropping below 30fps at all, as the R9 280 is slightly faster then the 760 in most cases :
(7950 boost is the same chip and VRAM as R9280 different clock depending on vendor)
Then I would suggest that 280 is minimum on the AMD side for ultra (Not saying there's not people playing with lesser cards).
On Newegg I see that GTX 760's are going for about $250 and R9 280 are about $300. I had an MSI Twin Frozr 7950 before my current 780 and it overclocked like a champ as did most of them I have heard, I sold it in December during the coin craze for more then I paid for it and got my 780.
If you will overclock then I would personally pay the extra 50 and get an R9 280 to get 280x like performance, if not overclocking I would go GTX 760 and get an EVGA ACX version, as that's what I was recommended on here and I can say I'm very pleased with the cooler and its comforting to know that they have such great customer service as well as the 'Step up' program where you have 3 months when you can pay the difference in case another faster card is released.
Of course if you have more to spend then that's up to you, I would avoid the 4GB versions of the 760/770 because IMO it is still unclear whether there is any benefit at all to having double the VRAM on these cards. This is a subject of some debate on here though but you know which way I'm leaning at least.
Also worth bearing in mind that Nvidia are releasing Maxwell 800 series GPU's later in the year last I heard Q3 this year. If you can hang on that long it may be worth it to get more for your money.