At stock speeds, it's slightly less powerful than the Core i5 750 quad core processor. (the 965 is slightly faster than the i5). Here's a convenient chart: http://www.cpubenchmark.net/cpu_lookup.php?cpu=AMD+Phenom+II+X4+955
It would probably be compared to the Core i7-930 Bloomfield but wouldn't really be the equivalent because of Intel's Turbo Boost and Hyper Threading technologies.
Before Overclocking: it's neck and neck with a Intel Q9650 in the raw bench marks.The numbers are inconsequential as you can bump the black editions up a bit in the form of overclocking.I wouldn't be overly amazed if an overclocked 955 black edition with the right video card didn't come withing 20fps of an I7 920 or 940 on similar hardware In a gaming test environment either.>Hope that helped.
top end of the core2quad range. with overclocking (that with a £60 h50 you can get almost 4 ghz out of that thing with good ram) easily cottending and beating i5 cores