Originally Posted by
HigoChumbo
No, you need two of the same model for sli to work (they can be from different manufacturers though).
If it's just for Warhammer, unless you are playing at huge resolutions, a 970 should be perfectly fine. Another option for you if you want to keep your 970 is to wait a bit until the prices drop (and they will after the release of the 1000 series) and get a second one for sli. I personally am not a fan of multiple gpus though. But again, with a 970 you should be covered for now, I'd personally wait a bit to step up.
Depends on your resolution, at 1080p that rig should be really good. Have you considered to overclock your CPU instead of buying new hardware?