I'll rephrase: The Athlon II 750K is probably better than any Phenom II x4 CPU when overclocking is considered. The x6s would still win in some well-threaded workloads quite significantly. Heck, even the Llano Athlon IIs can fight with the Phenom IIs when both are overclocked to the max.
With the modular architecture's affinity for very high frequencies, I have no doubt that these Athlon IIs can be pushed farther than a Phenom II x4 CPU can (let alone on the same power usage). Heck, with overclocking, even the FX-4100 can be close to a Phenom II x4. Make a CPU that has an ~15% performance per clock advantage and has even better overclocking ability due to lowered power consumption and it could do substantially better.