Recs.
Updated
This Titan X uses the old Maxwell architecture, which has been replaced by Pascal architecture in 2016. The card handles most games in 4K with very decent frames per second. 12 GB of video ram lets you easily use a setup with several monitors.
SpecsUpdate
Pros
Pro Good 4K performance for most games
Assassins Creed: Unity and Call of Duty: Advanced Warfare 2 both had some troubles running 4K games on the highest available settings: both manages just an average of 17 fps. Reducing the settings slightly boosted performance considerably in COD: Advanced Warfare 2, shot up to 86 fps minimum without FXAA 8X enabled, although dropping down to medium graphics in Assassins Creed Unity only brought the framerate up to 34 fps average (29 minimum).
Other titles like Dying Light ran at 40 fps (34 minimum), Evolve ran at 39 fps (minimum 31), Grid Autosport (with 8X AA) ran at 74 fps (61 minimum), and Shadow of Mordor ran at 66 fps (minimum 35).
Pro Can be cooled by custom means
There are available bracket/liquid cooling combos, which can keep this card much cooler than just the stock cooling system would be able to do. One customer on NewEgg.com claims that their Asus GTX Titan X never warms up more than 50 degrees Celsius after implamenting one of these solutions.
Cons
Con Very expensive
The new GTX 1080 cards offer great performance as well at a fraction of the cost of this Asus GTX Titan X.