I don't think there week intotal 1550mhz core Clock with 2GB 8000Mhz
I hope you understand that clock speed and memory is not additive (i see you're doing 775MHz x2 cards to get 1550MHz). Also when you have two 1GB cards you only have 1GB of memory usable not 2GB.
If the game is coded to utilize more then a single GPU, then the game will utilze the processing power of both cards as needed. But both cards do not add together and become like one single powerful card.