[advice] for new PSU

Hello,

here its my PC specifications:
i7 core 3.99 Ghz @ 920 OC , GIGABYTE EX58-UD3R v 1.0 , CORSAIR TRX6G1866C9DF 6 GB RAM @ 700+ MHz OC , GIGABYTE GTX 295 , 2xWD 1TB 7200 rpm HDD + WD 300 GB 10000 rpm , EVEREST PRO PSU @ 1100 watt, GIGABYTE AURORA 570 BLACK TOWER ATX CASE, GIGABYTE 3D Galaxy II cooling system.
also I connect some USP devices like head set, mouse, keyboard and 2 usb HDD without power adapter
and that EVEREST PRO PSU doesn't work anymore
is it necessary to get 900+ PSU watt for such componenets because friend told me that I can run my system with 650 watt PSU but am fraid of unstablity because of the OC CPU and RAM

so what power supply should I get   ???