Not sure if it makes a whole lot of difference, I'm using -w 256 --thread-concurrency 8192 --gpu-memclock 1500 --gpu-engine 1100.  That gets me between 4.0 to 4.2mhash/s per 280x.  I didn't install anything extra other than the 14.6 RC drivers from guru3d.

Anyone have any ideas on what is a good speed for a 290x?  I'm using 14.6 drivers and the .cl files posted from someone on here and I'm getting 5.9Mhash/s.

core 1065
mem 1250
intensity 17
threads 27400
worksize 256

If I increase memory to 1500 I can get it up to 6.1Mhash/s but it gets a little unstable.