Soldato
@ 1550Mhz the 970 is about 15% quicker than a stock 980, i would also question if a 980 can run 1550Mhz 24/7, most good AIB 970's have the same and beefed up 980 PCB's only they use a bit less power so they can get a bit higher, mine for example has the same 8 + 6 Pin WF-OC PCB and cooler as the 980.
As for the 980TI, its about 25% quicker than a stock 980, its probably about 15% short, but the 980TI is a monster clocker too.
So the 480 would actually be faster than a stock 980ti in this game at 1080p anyway.