From your example, I take it Athlon II X2 is the HD 5670 and the RAM is the memory of the GPU, an Athlon II X2 with 8GB RAM is overkill. Is this the same case with HD 5670 1 GB? So 512 MB version really does performs as well as 1 GB?
And yes, you're right, I dont quite understand about GPUs well enough.
Thanks for your replies.