do I need a better powering supply??

[Alleyzz]

if my power supply give 300w. I will buy a new graphic card (GEFORCE N750TI TF 2GD5/OC) do I need a better power supply?

 

[_Blank]

Yes,you better get an 450 watt or more if you plan on upgrading in the near future.

 

[juanjostorreshernndez]

You are under minimun recommended which is 350W:http://www.realhardtechx.com/index_archivos/Page362.htm
But the most important thing is having not a generic PSU, cause it may deliver much less power than labeled(300).
So you must have at least a 350W good branded certified PSU in order to be safe.
What is your PSU brand ?