Crossfire with kaveri?

what is the highest gpu i can crossfire a kaveri 7850k?

R7 250

Yeah the R7 750 is the highest thing you can run dual graphics with and I don't recommend it at all. The price to pwerformance ration is pretty pathetic. 

Better off buying the cheaper Athlon 760k and pairing it with a higher end GPU like an R9 270. Much better value there and may even be cheaper overall.