My system specs should be in my signature. I am planning to add a Sapphire Toxic HD 5850 to the system. Is my power supply enough? I am not planning to add anymore devices to the system.
you will be fine, you have a very good PSU that has 650w of continuous power. the following system topped off at 550w at load with the ATI 5850 in CF
CPU: Intel Core i7-920 @ 3.33GHz
Motherboard: Intel DX58SO (Intel X58)
Chipset Drivers: Intel 126.96.36.1995 (Intel)
Hard Disk: Intel X25-M SSD (80GB)
Memory: Patriot Viper DDR3-1333 3 x 2GB (7-7-7-20)