Apple iMac with Retina 5K display
If you already know that you want an Apple computer for editing, then this is definitely the pick for you. It has an Intel i5 quad-core processor, though it can be upgraded to an i7, as well as 8GB of DDR3 RAM that you can increase to up to 32GB of memory. This computer comes with a 2TB hard drive, which can be upgraded to a 3TB hard drive or one that uses flash memory.
The default AMD Radeon R9 M395 video card is good with 2GB of memory, plus you can upgrade that to an M395X with 4GB of video RAM instead. You can also get a number of software programs from Apple which are great for performing all kinds of editing with streamlined functionality and guaranteed system compatibility. If you're not an Apple fan, then you still might consider this option for its absolutely gorgeous retina 5K display which is probably the best looking monitor currently available on the market.