EXPERIMENTAL: A new way of setting intensity; introducing xintensity!
All of this is credited to ArGee of RGMiner, he did the initial ground work for this setting.

This new setting allows for a much finer grained intensity setting and also opens up for dual gpu threads on devices not previously able to. Note: make sure to use lower thread-concurrency values when you increase cpu threads.

Intensity is currently used to spawn GPU threads as a simple 2^value setting.
  I:13 =    8192 threads
  I:15 =   32768 threads
  I:17 =  131072 threads
  I:18 =  262144 threads
  I:19 =  524288 threads
  I:20 = 1048576 threads
Notice how the higher settings increase thread count tremendously.

Now enter the xintensity setting (Yes, I am a genius with my naming convention!).
It is simply a shader multiplier, obviously based on the amount of shaders you got on a card, this should allow the same value to scale with different card models.
   6970 with 1536 shaders: xI:64 = 98304 threads
R9 280X with 2048 shaders: xI:64 = 131072 threads
 R9 290 with 2560 shaders: xI:64 = 180224 threads
R9 290X with 2816 shaders: xI:64 = 163840 threads

   6970 with 1536 shaders: xI:300 = 460800 threads
R9 280X with 2048 shaders: xI:300 = 614400 threads
 R9 290 with 2560 shaders: xI:300 = 768000 threads
R9 290X with 2816 shaders: xI:300 = 844800 threads

It's now much easier to control thread intensity and it potentially allows for a uniform way of setting the intensity on your system. I'm very interested in constructive feedback, as I do not have access to a lot of different card models.

This change has been tested on 6970, R9 290, R9 290X - all with equal or a little better speeds than regular intensity setting after a little tuning, but your mileage may vary. Don't fret it, if this doesn't work for you, the regular intensity setting is still available.