Just remeber, as it has been said MANY times in multiple threads, when purchasing a PSU it's not only the wattage you need to look at, you also need to make sure the amperage ratings on the different rails are high enough (high the better).
Like LeeJend said, if you have a high end system you will most likely need soemthing with 17A or higher otherwise you make have issues.
The issue you described my be a sympton of an overworked PSU and using something thats rated for a P3 won't help with troubleshooting as it's ratings may be lower then your current one.