Swapping a R9 270 for GTX 690 for 180 €. Worth it?

In my opinion, no, even though the GTX 690 is a vastly more powerful card.

The two big problems with the GTX 690 is the lack of VRAM and the fact that it's treated as an SLI configuration. Personally, I'd sell the R9 270 and use that money alongside the €180 to buy a GTX 1070 or a GTX 970.
 
Well i had a msi r9 270x and swapped it for a gtx 690 because i dont have that much money. And i need to say i am really happy about it. I run the most games like doom on max between 40 to 80 fps.

The only thing is that the card gets kinda hot between 70 to 85 Degreese celcius.
If the tempature is not a problem for you i would upgrade the card.

I bought mine for €160,- but btween 200-140 it is a good deal for this GPU.

Hope i could help you