For converting movies, the bottleneck is usually the CPU. Typically for gaming, that is going to be your graphics card and RAM. The most important thing to know when deciding on an upgrade part is to determine what your bottleneck is. For comparative shopping between brands, you can look at either multiple benchmarks for a given application, or a CPU hierarchy chart for overall general speed comparisons. The reason you cannot compare cores alone is because for cores to be useful, the program you want to speed up must support multiple cores in an efficient manner, if it is not a multi-threaded application, the extra cores will be no benefit at all. Another reason is that some processors have more cache memory which is has a very fast access time to as opposed to its ability to access RAM. One reason you cannot only compare GHz is that GHz is a measure of cycles per second, and some processors can do more in one cycle that another processor my require two cycles to perform. Raw GHz alone cannot be used to determine a better processor, nor the number of cores.

What is a cpu meter