They're all good for gaming at the resolution you use, but not for 4 years. The 7950 is the 'best' in terms of power, and can be overclocked really easily to give even better performance. The 7870 is a good card, but it's priced far too high to be an option.
The 7850 is a decent card for your resolution, but it won't have 4 years of life in it, unless you don't mind putting up with very low graphics settings in the future.
So in short, 7950>7870>7850 in terms of performance. The rest depends on what you're willing to spend, and the other components on your PC (CPU, and PSU). If you can find a GTX670 for ~300EUR in the Netherlands then that would also be a very good GPU, both the GTX670 and HD7950 are overkill for your resolution at the moment, but they'll last a good while too.