What's a good machine for iPhone development 2015/2016?

so I'm PC user Windows.
but I used Mac before, now i'm planning on learning C, object-c so I can create my apps you know have some fun.
There is a lot of questions in here but i find that Old.

So what I want to know is what machines are good/The Beast for now in 2015/2016 so i can work with Xcode without problems.
My budget is 4 thousand dollars.

via Chebli Mohamed