TechSpot looked at the Intel Core 2 Duo E6300 and E6700 Overclocking Performance:

The E6300 offered even more overclocking headroom, as it went from 1.86GHz to 3.03GHz using nothing more than the XP-120 with a 2500-RPM 120mm fan. The best part is these clock speeds can still be achieved with basic PC-6400 memory, as the P5W DH Deluxe offers a wide range of ratios for the memory. To obtain the maximum performance possible however, at least DDR2-900 memory will be required.

Something to notice is that even at 3.66GHz using a 1.400 voltage, the E6700 processor never exceeded 45 degrees when under load. Given a standard Pentium 4 660 processor would have a hard time achieving this, I was impressed to find the overclocked E6700 operating at such reasonable temperatures. The E6300 also reached roughly 45 degrees when stress testing, and at no time either overclocked system came unstuck.

Naturally, the performance of the overclocked Core 2 Duo E6700 processor was astonishing, as it is breathtaking at 2.66GHz, let alone 3.66GHz. For those seeking the ultimate Core 2 Duo experience the 4MB L2 Cache processors are a must as the additional cache really does make a difference when overclocking. However, the E6300 is a seriously good value processor, offering the best possible bang for your buck at just $180. Overclocked, the E6300 is somewhat comparable to the much more expensive E6700 as it was faster and then slower, depending on the application.