Yes, i checked your PSU and it will run your setup with the 7850 quite easily.
It is an 80 Plus certified PSU, which means it will have greater than 80% efficiency for loads upto 100%.
Also there are two 6 Pin PCI-E connectors, out of which one will be required for the 7850.
The PSU has two +12V railings each with 20A, which means roughly 2 x (12V x 20A) = 480W on your +12V.(Its just an assumption, power on two +12V railings isnt actually simply added in realtime).
The +12V is what gives power to your Motherboard,CPU and So On.
So simply, that is a good PSU and it will run the entire setup very well
To answer your second question, THe i5 650 has a TDP of 73W, as your running it OC'd, i would give it a 75W - 80W.
The TDP for the 7850 is measured at roughly 110W.
Then Comes in your RAM, HDD, DVD drives and so on. Lets give it a headroom of 100W.
80 + 110 + 100 = 290W (This is way more than the what the actual readings would be, just assumptions).
SO basically you will be left with another 150 to 200 Watts to spare.