What is the make model of your pc?
What is the make/model of your two monitors?
What is your objective in adding a third?
First, see what options you have to attach a third screen to your motherboard and the HD630 display adapter.
Look on the back of your pc and enumerate the display outputs you have.
Enumerate the inputs acceptable to your monitors.
What are you using now, and what, if any is the type of the extra port.
From a performance point of view, HD630 is reasonable capable for HD movie playback and three displays.
If you are not happy with the performance, you should be able to add in a discrete graphics card that will do the job. A GT1030 will run with any psu.