How much could I get if I was to sell this??

[Rufcsam]

Case
CORSAIR SPEC-ALPHA MID TOWER GAMING CASE - BLACK/RED
Processor (CPU)
Intel® Core™ i7 Quad Core Processor i7-6700 (3.4GHz) 8MB Cache
Motherboard
ASUS® Z170-P: ATX, LG1151, USB 3.0, SATA 6GBs
Memory (RAM)
16GB HyperX FURY DDR4 2133MHz (2 x 8GB)
Graphics Card
3GB NVIDIA GEFORCE GTX 1060 - DVI, HDMI, 3 x DP
1st Storage Drive
1TB SEAGATE BARRACUDA SATA-III 3.5" HDD, 6GB/s, 7200RPM, 64MB CACHE
2nd Storage Drive
1TB SEAGATE BARRACUDA SATA-III 3.5" HDD, 6GB/s, 7200RPM, 64MB CACHE
External DVD/BLU-RAY Drive
8x Slim USB 2.0 External DVD-RW
Power Supply
CORSAIR 550W VS SERIES™ VS-550 POWER SUPPLY
Power Cable
1 x 1 Metre UK Power Cable (Kettle Lead)
Processor Cooling
STANDARD CPU COOLER
Thermal Paste
STANDARD THERMAL PASTE FOR SUFFICIENT COOLING
Sound Card
ONBOARD 6 CHANNEL (5.1) HIGH DEF AUDIO (AS STANDARD)
Wireless/Wired Networking
10/100/1000 GIGABIT LAN PORT (Wi-Fi NOT INCLUDED)
USB/Thunderbolt Options
MIN. 2 x USB 3.0 & 2 x USB 2.0 PORTS @ BACK PANEL + MIN. 2 FRONT PORTS
Operating System
Windows 10 Home 64 Bit - inc. Single Licence
Operating System Language
United Kingdom - English Language
Windows Recovery Media
Windows 10 (64-bit) DVD with paper sleeve

 

[Rufcsam]

I have also installed WiFi to it

 

[Oussebon]

However much someone it willing to pay for it.

Even though it's a PC Specialist system (I assume it is) we can't advise about selling on this forum.

In general terms, hardware can lose value quite quickly, so whatever you get it's likely to be less than what you paid by a lot. Check for what similar specs on ebay seem to be selling for 2nd hand I guess. And check the individual components, it might always be that selling those individually nets you more.