This is what i would do with ~1000€. May i ask what you do with this PC though? If Gaming, what games do you typically play and at what resolution (1080p, 4K, etc)?
List at the moment: (Please note this is in Germany, you stated Euros but what country?)
PCPartPicker part list:
https://de.pcpartpicker.com/list/GnHM7h
Price breakdown by merchant: https://de.pcpartpicker.com/list/GnHM7h/by_merchant/
CPU: AMD - Ryzen 5 1600 3.2GHz 6-Core Processor (€213.99 @ Amazon Deutschland)
Motherboard: Asus - PRIME B350-PLUS ATX AM4 Motherboard (€93.08 @ Amazon Deutschland)
Memory: Corsair - Vengeance LPX 16GB (2 x 8GB) DDR4-3000 Memory (€130.99 @ Amazon Deutschland)
Storage: SanDisk - SSD PLUS 240GB 2.5" Solid State Drive (€81.99 @ Amazon Deutschland)
Video Card: Asus - GeForce GTX 1070 8GB Dual Series Video Card (€414.99 @ Amazon Deutschland)
Total: €935.04
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-06-19 12:45 CEST+0200
You're XFX TS 550 should handle this upgrade fine but if you feel the need you have enough left over under 1000 to add a brand new Power Supply if your current is older than 4-5 years or you simply want a better one. If you're a moderate-high Overclocking i suggest using the left over budget towards a X370 Motherboard otherwise you could consider a bigger/faster SSD. Hope this helps