I have build one computer and want to do it again! Had some regrets for the first time(parts didn't 100% fit in the case, I had to cut two parts out with a Dremel to get the GPU in). That was before I knew about this website and it compatibility checker.
Anyways love it and it is epic. Games like a beast and for school it is great too.
I would recommend if you are looking to get a gaming pc to build it yourself!!!!! There are many websites and stores that will build it for you such as Digital Storm or Alienware, however when you build your own computer, you have felt a sense of accomplishment and great relief when it boots up. Also, if you think about it, no other computer is the same as yours when you build it. You picked the parts and assembled it the best you could and that's what makes it special.
When you buy a gaming pc (I don't oppose it) you don't have the sense of accomplishment of building it, but for a little extra money it will save you hours of time and effort building your pc.