I have a samsung syncmaster 733nw monitor.I'm buying amd r9 270 gpu.Do i need to change my monitor?I actually want to know that if the monitor is an issue in case of a graphics card?
You'd be fine for now, no need to change monitor for any video card. However, the impact would be that your monitor won't show the resolutions and or refresh rates, that that video card is capable of.
if you can link us which specific GPU you plan to get, we can tell you if it has a VGA output or not. The one from your computer will not be the one from your GPU.