Found 2 exchanges where Stacks is traded for EUR. According to the data on 3 September the most optimal price to exchange STX for EUR is €0.235 for 1 Stacks. This rate is fixed at Bitvavo at the maximum trading volume of the pair STX/EUR - 230.7 ths. EUR.
The maximum daily trading volume is observed in the STX/KRW trading pair at Upbit and reaches € 2 778 509.4 (0.52% of the exchange's total trading volumes) at the price € 0.228 per 1 STX.
The minimum price to buy STX for EUR is 0.22 - on the exchange Bit2Me.
The maximum price to buy STX/EUR is 0.235 - on the exchange Bitvavo.
Warning: some STX markets show an abnormally wide spread — those quotes may be unreliable (thin liquidity or off-market trades). Cross-check the volume against several venues.