Yeah.. If only it wasn't all a big secret.. 
In TilDeath's defense I've seen too many in this forum overspend on RAM when it won't provide any benefit over a slower version. Similarly, many feel the highest end video card will solve all their problems when in fact, they are just going to be bottlenecked by the CPU. Sure you can put those components together and the system will run but decreasing the RAM and GPU to spend more on the CPU will improve the overall system performance and provide a much more satisfying experience with the finished unit.
This isn't even taking into consideration future upgrade paths, which can extend the life of the base purchase for several years.
I agree that building a balanced system isn't just slapping components together. It takes a lot of time and research or experience to get the most out of each component in a well balanced system. I spent three months researching each of the components that went into my system and I'm very happy with the results I obtained.
Of course we have some very experienced people in this forum that can recommend parts and be knowledgable enough to keep a system in balance drastically reducing the time commitment needed by the future builder. Then, there are others who aren't so adept.