Just build your own PC. Even if somebody isn't familiar with doing it, with just a moderate amount of research it isn't hard to learn. You can get all the parts you want, (Or at least all the parts that fit in the price you're willing to spend on them.), and it's cheaper and better most of the time than buying a pre-built PC. About the only downside is if you really need some of the bundled software that often comes with pre-built PCs you would need to spend extra on if you built your own. There are even websites that will help you with price and knowing if everything is compatible beforehand.
About a year ago I built my first PC and it only took me five or six hours, even adding things a water cooling system and internal light strips.