Upgraded the old 2012 Macbook Pro Retina 15" to the same thing, just late 2015 model with 16GB RAM (double), 512GB SSD (double), and a Radeon R9 M370X (probably almost double).
Upgraded my Vizio 37" 1080p panel to the LG 43" UHD (2160p) panel. Which is actually smaller due to a nearly non-existent bezel; and I can store stuff under it!
Same monitors and driver: Yamaha HS7s driven by a Steinberg UR22. Same expansion hub: Anker 7-port USB 3.0 x 2 fast charge (1.5A + 2.1A). Same peripherals, intstruments, and so forth.
The purpose of this upgrade was to be able to run 2160p at 60Hz reliably for extra room when working with timeline and panel-based applications. The extra space really helps and once you get over the tiny-ness of everything, you're hooked. It's much easier and less expensive than multiple displays.
If anyone is planning on going 4K/UHD for computing purposes, I would highly suggest a screen larger than 40". Any smaller, and most ordinary objects become distorted and would require a magnifying glass in order to enjoy.
The forum looks hilarious...