If i have a high capacity PSU let's say 750w PSU, and my system only need maybe like 450-550w or somewhere in between. What will happen? Is is good or not? Is it necessary to change my psu to 550-650w? Thank you the responses.
A system will only use as much power as it needs. You could run a 1600w power supply and use onboard graphics and the only bad thing that would happen is you would waste money on a 1600w power supply.