The X4 965 Is Basically An Already Overclocked 955, No Need To Spend The Extra Money For It.
The 970 Is Again Clocked Higher At 3.5 Ghz, But It Uses 125W Power Where as the c3 Stepping version of the 955 will use only 95W.
Performance wise, there will be very very less difference among the three.
Pick The Phenom II X4 955 Black Edition C3 Version And The Overclock It After Buying A New Cooler.
And Yes, Corsair Is A Good Brand, Its One The Most Trusted PSU's Around The World. It Will Handle Everything Pretty Good.