If you're going to buy the parts and have someone else build it, you could consider having one built by CyberpowerPC. You can pick make/model of most components. They have a pretty big selection. The only thing I don't like is you can't pick the make/model of HDD. Because of that, I'd say equip it with an SSD and pick up your own WD Black HDD and drop it in there. CyberpowerPC offers a 3-year warranty, but they also ship you the box all of your components came in and you can register the parts individually. They do a good job.
On the other hand, even if you've never built one, you'll be surprised at how easy it is. It's also a pretty rewarding experience.