Well a Z97 board will make a difference, certainly make it more appealing to buyers and validates the cooler.
Problem with $1500:
https://pcpartpicker.com/list/NjTjKZ , all new parts, and better.
So you might be able to ask $1000, but don't expect to get it.
You might manage something like $150 for the monitor. Not exactly the most desirable a 5ms TN Panel, and they can be bought new for around $200.
Keyboard, Mouse and Headset, someone willing to buy them certainly won't pay top dollar.
Really nothing wrong with the system. From experience I can tell you that the CPU performance difference between an overclocked 4770k and an i7-7700k is only 20%, and that won't translate directly into gaming performance. If you are selling to build a new rig, you could just pick up a new GPU and keep on rolling.
I upgraded only so I could make my 4770k available for another system.