DEFINITELY!
I am using two 970 GTXs and my old quadro k4000.. while the quadro kicks ass with CUDA, it is actually half as fast as the 970's for this sort of openCL calculation. All together though, the system hauls ass. Add everything you can. Alexey and the team did an awesome job making Photoscan utilize every possible ounce of power IMHO. Hope it helps!