Overclocked gtx460 or ati 6870

If you do care about PhysX and all, then the GTX460 is a good choice. Obviuous fact is HD6870 performs better than that. Absolute tops would be the HD6950 if you can stretch it to $300.

Sorry i forgot to add that i will prob buy a Asus 19 inch hd moniter,with max resolution at 1440x900. will gtx 460 or 6870 be able to give atleast 60 FPS on most highend games like metro 233,crysis warhead,black ops... or will a lower card will do for dis resolution,like the ati 5770?

For the resolution you mention, the HD5770 should be enough. If you think about going for a bigger monitor then i think you stick to your current choices. Otherwise 5770 does the job adequately well.

You would be able to see good frame rates, but that is not that important, as long as you don't see any stuttering it shouldn't be a problem.

60fps on metro2033 even at that resolution is a pipe dream (if its dx11) even with a gtx460/6870, much less if you're going 5770.