My settings for R9 290X

 --scrypt -o stratum+tcp://us.clevermining.com:3333 -u blablabla -p anything -w 256 -v 1 -I 18 -g 1 --thread-concurrency 32765 --log 5 --gpu-fan 80 --gpu-powertune 20 --gpu-memclock 1500 --gpu-engine 1000 --lookup-gap 2 --api-port 4028 --temp-target 80 --temp-overheat 95 --temp-cutoff 97 --queue 1

I reach 900khs: http://d.pr/i/zSOn

Try it because 290 is quite similar to 290X.

Maybe set --gpu-engine 920 and --gpu-memclock 1400.