The Dell P2715Q is the best 4K monitor for most people because its display quality is exceptional, its price is reasonable, it has all the connections you’ll need for your PC (and USB devices), it comes with a highly adjustable ergonomic stand and a VESA mount, and it uses single-stream transport for its DisplayPort connection-much better than cheaper (or older) multi-stream transport monitors. You picked the same monitor that was picked as the ' best 4K monitor ' by The Wirecutter review site (that linked article just came out this morning, I was just reading it).
Dell 27 Ultra HD 4K Monitor – P2715Q at $589 (3 yr warranty), IPS.