How bigger power supply do I need?

You have plenty of power for your listed configuration.

No problem with your 650.

yeah, you could probably put another 4850 in there with that much power.

just a quick bit of advice, have a look on the power supply's label and see if it lists the total available watts on the 12V rails thats the number you want to look at

from what ive read that PSU is a cheap generic rebranded shaw psu and probly wont be able to deliver anywhere close to 650 watts on the 12v rails

just going by the label itself and using a calculater the 3.3 and 5v rails add up to 345 watts leaving 305 for the 12v rail and thats only if it can deliver the full 650 watts.

granted all this info is based on my own research but im pretty sure its accurate if i am wrong im sure somebody will correct me

but just be careful about adding to much to your system generic psus can sometimes burn out easily and can take your comp with them

skimp out on a vid card skimp out on a processor hell even skimp out on a keyboard and mouse but never skimp out on a power supply

oh and to answer the question even though its a bit old, a good quality 350-500 watt will handle that set up

no probs, a quality 550 could take that

lol a quality 400w could take it  

This is the link that i use for that:
http://extreme.outervision.com/psucalculatorlite.jsp