Ι intend το build a new PC within the next few weeks and after a lot of research i decided that a sapphire HD 5850 would be an excellent choice for gaming. The problem is that i dont like big monitors so i plan to use my old one that has maximum res of 1280-1024. The cpu will be a phenom x4 955. Will my cpu be overpowering the gpu while gaming at that res?
No, your GPU would be overkill for your res. I would suspect there's no such thing as CPU overpowering GPU. More like GPU being bottlenecked by CPU (not in your case). If you were using the 5850 at my res, 1680x1050. Then the 5850 would be a good choice, but your not. Your infact using a res that the GTX460 would be the good way to go, by the by, don't associate the GTX 460 with the problems the 470 and 480 face. The 460 is pretty much perfected where the 470 and 480 failed. Power, temps, etc. It is the most logical choice for you at 200$. If you said high res like my 1680x1050, the 5850 would be good because it can be OC'd to a 5870 stock performance. But no, the 460 is actually the best choice for you. If you don't like the green team.
The red team has the 5770 which would probably be good enough as 1280x1204 doesn't stress GPU that much, and the 5770 can still be OC'd. Plus the 5770's are only 140$ right now on newegg.
while reading some of the threads in the forum, i understood ( or misunderstood to be honest ) that it is possible when gaming at low res, a high end video card will not work in its maximum potential in the same time the cpu will try to do the work of the video card resulting in low framerates and low performance. That is what i meant.( my english are not very good so forgive me if Ι got it wrong)
The cpu at that res will be fine, its still more for a lower res regardless.
Since the fps increase due to lessor demand on the gpu, more work is required by the cpu, but in this case, its fine, and possibly overkill as suggested earlier