I have one server computer for sale. It is the one [rs2.fi] used for running [rs2.fi] Komppania Törni servers, but we have now moved to another computer, not because of the server power but due to ISP changes.
i7-4770K clocked to 4.3 (multiplier clocked only, no voltage change, so it is 100% stable)
Asus Z-87K motherboard (no bells and whistles, but robust)
16 GB DDR3 (CL9 aka fast)
Modular PSU (Corsair AX, very good and less than 1 y old)
120 GB SSD (Kingston, basic)
2 x 1 TB HDD (Raided)
AIO water cooler (Corsair)
Intel CT Network card (configured to work with GameServer type packets)
Asus G210 GPU (handy if you want to connect to a KVM switch)
Legitimate Windows 2012 R2 Server OS license
Fractal Define R5 case
But now comes the BIG but
The computer is in Finland. I have really no idea how much the shipping cost will be even inside EU. And I don't even know your location, Mallic.