Which GPU should I choose? Help!

I would get the Gigabyte GTX 560Ti SOC.

so is your budget 120 euros? and are you sure you want used parts?

you can compare the gpus here. http://www.hwcompare.com/ compare them and choose the best

This should help you decide. Also if you have specific games you like playing, look for benchs in those games.

I would choose Gigabyte GTX 560Ti SOC.

buy used. Picked up a 550 ti for 60 bucks awhile back. Still runs strong

You should get GTX 660 if you have the money, I got one on ebay last week and it was 160 euros.
But if you don't, I'd say get a GTX 560ti or a HD 7770

Oh, important thing: make sure your PSU has the right amount of PCI-E power connectors for your card of choice.

Gigabyte AMD Radeon HD 7850 2 GB GDDR5 DVI-I/HDMI/2x mini-Displayport PCI-Express 3.0 Graphic Card GV-R785OC-2GD around $185

What're your other specs, include PSU.

your choice is clear! get a Riva TNT 2

32-bit frame buffer for better quality visuals at higher resolutions, 32-bit color for more realistic colors, and a 32-bit Z/stencil buffer for incredible 3D effects FUCK YEAH

Out of those, probably either of the latter two. Google a comparison of the two. I think in this case the 560 might be a little faster than HD 5870, as the 560 was designed to go against HD 6000 series.