Benchmarking a single component is good for a idea how something will perform. But when building a system you need to benchmark the system as a whole. You can put the fastest processor in a system but the MB, Video Card, Memory and PSU used don't play nicely together and you will not get the best scores. To spec a system you need to have more info at your fingertips then what review sites provide.
If you want to see how well your system performs overall you want to look at the different 3Dmark software from FutureMark. It has become an industry standard for benchmarking completed systems. You can then post your stats on the ORB site for people to see and for your own comparisons.
TD