Everyone wanted the E6600, so when it was released, they got bought up very quickly. Why? The E6300/6400 have 2mb of L2, while the E6600/6700/X6800 have 4mb L2. Most people wanted the extra cache since the clock speed difference could easily be made up by overclocking. Since the E6600 was the cheapest one with 4mb, they sold out within hours.