I am having 3 Asus R9 280x cards and  getting 5.35M/H using the following config

cgminer --scrypt-jane --sj-nfmin 4 --sj-nfmax 30 --sj-time 1395744444 -o stratum +tcp://stratum.eu.grp.hardcoreminers.com:3019 -u xxxx -p xxxx -w 256,256,256 -I 8,8,8 -g 2 --lookup-gap 2,2,2 --gpu-powertune -20,-20,-20 --temp-overheat 85,85,85 --temp-cutoff 90,90,90 --gpu-memclock 1500,1500,1500 --gpu-engine 1000,1000,1000 --thread-concurrency 8191,8191,8191

Hope That helps some one

If it helps please send some Graphenes  to gYTKgCizziPSijm5i6V4mfWbMwE4c6WQ4n