With 5750, at that resolution, you will be able to play all games maximized including CRYSIS
Not really. As you can see here it averages 20 fps with Crysis fully maxed at 1280x1024 with a minimum of 14 fps.
His resolution is slightly lower but for smooth game play a 30 fps minimum is generally the goal and it will still be far from that.
That said trying to max out Crysis is a poor way to choose a video card. The HD5750 should be very good although here at least(the US) it's a bit sketchy value wise compared to the significantly cheaper HD4850. I don't know the prices of those cards there however so that may be irrelevant.