I'd go with:
CPU: Intel Pentium G4560 2x 3.50GHz So.1151 BOX (64 €)
CPU Cooler: Be quiet! Shadow Rock slim (39 €)
Motherboard:Gigabyte GA-B250M-D3H (77 €)
Memory: 8GB Corsair Vengeance LPX DDR4-2133 DIMM CL13 Dual Kit (71 €)
Storage: Samsung - 850 EVO-Series 250GB 2.5" Solid State Drive (90 €)
Case: Fractal Design Define R5 (90 €)
Power Supply: 500 Watt be quiet! Pure Power 10 CM Modular 80+ Silver (66 €)
-----------------------------------------------------------------------------------------
SUM: 497 €
This would be silent and elegant build, ready for future update, If you choose to upgrade someday. It looks like coffee lake will support LGA 1151 after all, so you are looking at 6 core / 12 threats update potential.