I've got a corsair 600W should I boost up the power supply to 700W, or keep it as is not to over power the computer? I wouldn't say I would be playing games for more than an hour a day, maybe 5 hours a week.
650W is recommended but you might be o.k. i wouldn't risk it but to each his/her own.
You might be able to run it, but if you can, it'll be running at near 100%, which is something that you wouldn't want happening all the time. You always want headroom, as PSU's slowly degrade. Maybe your 600W is now only pushing out 590W, as that comes with age. Also running it at close to 100% all the time will make the fan and itself die alot quicker.