I work with two different brands (Kingston and GeIL) of RAM in one of my comps (with Socket 939 of course), and it gives me dual channel... I have never encountered any stability problems whatsoever...
These are 2x 512MB sticks however, so YMMV if you're going to use all four of your memory slots... You could get into troubles there, not because of the memory, but b/c of the CPU and mobo not being able to handle it very well (downclocked mem etc.)...
If it's possible to stick with the same KingMax modules, I would do so, but otherwise the memory itself should be fine...