The GTX 750 Ti graphics chipset is an excellent choice at the 170 Euors price range, it would be my pick at that range.
You might want to checkout the PNY VCGGTX750T2XPB-OC GeForce GTX 750 Ti 2GB. Same base chipset, but this one might be a little faster. Not sure if it will be that much of a noticeable difference though.
AMD Radeon HD 6670 vs MSI GeForce GTX 750 Ti
You will notice a big different between these 2 cards. The games you could only play in Low graphic settings with the Radeon HD 6670 will now be running at Medium settings with the GTX 750 Ti. Some game that the HD 6670 could not run will now be playable.