It's a tough one to judge, as you need someone who wants the exact same setup you have there.
I'm guessing the RAM is Sniper? What speed?
The problem is, someone can build a system that will rival/outperform that system for under $1,850 today.
PCPartPicker part list /
Price breakdown by merchant
CPU: AMD - Ryzen 7 2700X 3.7GHz 8-Core Processor ($309.89 @ Amazon)
Motherboard: MSI - X470 GAMING PLUS ATX AM4 Motherboard ($116.99 @ Amazon)
Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3000 Memory ($119.99 @ Newegg)
Storage: Crucial - MX500 1TB 2.5" Solid State Drive ($154.89 @ OutletPC)
Video Card: Gigabyte - GeForce GTX 1080 Ti 11GB Gaming OC 11G Video Card ($704.98 @ Newegg)
Power Supply: Corsair - TXM Gold 650W 80+ Gold Certified Semi-Modular ATX Power Supply ($89.89 @ OutletPC)
Operating System: Microsoft - Windows 10 Pro OEM 64-bit ($124.79 @ OutletPC)
Total: $1621.42
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-11-05 16:04 EST-0500
Yes, you have a custom loop.... Yes, you've overdone the RAM (for a gaming system)...... Realistically, even the CPU is overkill.
Essentially, you need a buyer who wants that exact config...... and doesn't want to put together a custom loop themselves.
The problem with that is:
1. Anybody interested in a custom loop, generally, will want to do it themselves.... Or pay a boutique builder. Not "some guy" from Craigslist.
2. The market for 32GB, 8c/16t and a 1080TI is pretty small.
On top of that, via Craigslist, you also need that person to be somewhat local to you.
Selling that as a "gaming rig" is not going to be doing you any favours...... with 8c/16t and 32GB, maybe market it as a production machine.
If I were you, I'd take it apart. Try to sell the EKWB stuff on it's own - much greater chance of a buyer looking for blocks/fittings, than someone preassembled.
Stick the stock coolers back on everything, and sell it as a production machine.
I'd imagine you could see the system (sans EKWB) for around $1,200 with a bit of luck.
The EKWB, entirely depends.