How many RAM you are use in your system? Please be sure you have for each card 4GB System-RAM, that was the only thning what increase my hasrates and makes it possible to configure higher thread-concurrencys. f.e. 2 cards minnimum of 8GB RAM
We use only 4G ram for system. We still don't use 290 for mining. Hope that your info can help other miners

I can confirm that 3 X R9 290 don't run on 4 GB RAM. I only get a speed of 264 KH/s per card. I ordered 4 GB more RAM and will update tomorrow, if that rises the hash speed.