Overclocking my video card

I was wondering if there's a give and take relationship between the core and memory speeds. That is to say, that if I speed up my memory too high will I not be able to clock my core as high? Or are they completely independent of one another and as long as the speed of one is stable the other will not be adversely affected?

Pretty much independant. Heat will obviously factor into it, but in general terms, whack 'em both up as high as they'll go without

a) artifacts (memory too high)

b) lockup and/or geometry errors (core too high)

It's not like overclocking the CPU/RAM on your PC, don't worry