KINGSTON 4GB DDR3

I am mining with four Dataland R9  270X  cards using cgminer. The hashrate of this kind of card  can  reach more than 400KH/s per one.  But my rig can only reach about 300K per card, and the total WU is about 900K.  When i set the Intensity to more than 13, HW uprising quickly, so i only can set all four at 12.

how can i increase the hashrate of my rig.
BTW: i use the win7-32bit OS,  is win7-64bit better?

i've set the gpu-engine to 1000M.

is there any other para i can set in the cgminer.conf  to increase the rig's function?

BTW 
hardware as follows
MB   biostar   h81s
GPU   DATALAND  R9 270X   6PCS
CPU  G3220
MEM  KINGSTON 4GB

i installed the AMD_Catalyst_13.12_W7_W8_WHQL, but didnt installed the sdk, and there is someting wrong when i run the cgminer saying "Failed to init GPU thread 0 , disabling device 0"  "Error -61  clCreateBuffer(padBuffer8),decrease TC or increase LG",  can someone help me,thank u!