The CPU will drop to a 6x multiplier when it is does not need to run at full speed. This is part of intels speed step technology and perfectly normal. If you disable speed step in the bios then the speed/multiplier should then be as expected.
As for as graphics cards go, I and no expert. But I would say that as your 4870 x2 is two 4870 on the same board, Each with it's own 1Gb of memory this would cause CPU-z to "misreport" the memory size. As for the GPU speed, again this can be attribited to the ATI power saving features.