If you are sure that PC8000 kit will come with D9GKX, then i would take it.
D9GKX tend to do better CL4 overclock and respond good to high voltages, while being properly cooled. I prefer D9GKX do D9GMH but they are rarer than the late ones.
You don't have to worry about 8000C5 reaching 9600 clocks.
Where did you find then at those prices? I could even order one for myself.