If you aren't planning on overclocking then you might as well just go with the 2550, I don't really know if there is much of a difference between the 2. That leads me to say pick the cheaper one.
The i5-2550 may be better but if it is it isn't by much plus it can't be overclocked. The 2500k can be overclocked and can easily beat the 2550 even if it is better at stock clocks. Go with the 2500k
The i5-2550 may be better but if it is it isn't by much plus it can't be overclocked. The 2500k can be overclocked and can easily beat the 2550 even if it is better at stock clocks. Go with the 2500k
If you aren't planning on overclocking then you might as well just go with the 2550, I don't really know if there is much of a difference between the 2. That leads me to say pick the cheaper one.