For reference, my AMD 290x's top out at 373 H/s per gpu. 12.3, asm 1, intensity needs to be around 6. Anything else and it diminishes significantly.
http://image.prntscr.com/image/341d9b53d4614ab6af042b136a599d89.png
http://image.prntscr.com/image/341d9b53d4614ab6af042b136a599d89.png
I wonder why your 290x (373 h/s does so much more than my 380x (193 h/s).....
I need some different vid cards lol.290X has more processor cores and higher memory bandwidth.