i got through to kingston tech support. They said the same. Put the 1Gs in the color matched slots. I can add the 256, & it won't get used by the processor unless I've completely hit load limit, and then it doesn't help at only 256. It will run as an extra stick, not as dual, but the 1Gs will run as dual. The 256 will not hinder the 1Gs.
Oh good. Glad I was of some assistance :P
Yeah, I guess if you have it there, you may as well add it in. (As long as they are in the correct slots for dual channel).