Different RAM combination with ASUS triple channel (3x2GB & 2x4GB)

[lefteris]

I have the ASUS P6X58D Premium which has 2x3 slots for RAM DDR3.
I already have 3x2GB Corsair (CMT6GX3M3A2000C8) working fine and I want to add some more...
My settings are:
CPU: i7 930 @2.9GHz
FSB: 138MHz
FSB: DRAM 2:12
DRAM Frequency 830MHz
CAS, RAStoCAS, RAS: 8-8-8

The thing is that I have in my hands 2x4GB of HYPERX KINGSTON (KHX1600C9d3B1/4G).
It would be great if I could just add that to my system.
I am a little rusty with these things and I would appreciate your help.
Thanks.

 

[denis280]

First question, why! and is it for Gaming or normal use. ddr3 mixing will work.but you will downgrade to 1600 with the kingston in,you will be running 800mhz instead of 830mhz no big deal there

 

[lefteris]

No gaming... just normal and office use. A bit of photoshop, autocad and photo management.
Would it be better if I use 2x2GB Corsair (remove the 3rd dimm) and 2x4GB Kingston? I mean having 2 dual channel instead of one triple and one double?
Which benchmarks should I run to test the "penalty" for every day use?
Thanks again.