I'd recommend a macbook pro. I know people say "They're too expensive for the power you actually get" but i think just the overall quality of the parts and the OS in general is unparalleled. Besides, mac has always had a prominent place in music production. I got my macbook pro 13in retina with an upgraded 2.9ghz i5 and upgraded 16gb of RAM for about 1500.
Don't want to start this war here, but imho it's not just bells and whistles with Macs. There is also quite solid history of OS updates that messed up plugin compatibility that sometimes even developers had to step in. Last time with El.Captain. Apple doesn't give a damn about backward compatibility, so your ability to use certain plugins will depend only on their developers being active.
Windows has it's flaws too, but from my experience backward compatibility is stellar. Last year I've autoupdated from win7 to win10 and except two plugins needing re-authorisation everything worked like a charm.
Too lazy to build myself. So that's a non-option. Although I will want space for customization and additions.
Too bad. Pre-made gaming PC's are made for graphics power, meaning the CPU is on the same priority level as GPU. For music production, I'd spend a bit less on GPU and bit more on CPU as that's where all your rendering is happening. Having said that ... I'm running 2.5GHz quad core laptop CPU and it's more than enough.