To understand the prospects for quad-core performance, let me suggest reading a couple of our articles. My original review of the Core 2 Extreme QX6700 compared this quad-core processor's performance to a range of dual-core CPUs in a broad array of typical desktop apps. From this exercise, we learned that quad-cores benefits are rather limited, since even many multithreaded applications or tasks don't use more than two threads. I then turned my attention to more highly multithreaded applications in my Quad FX review, in which the QX6700 was prominently featured. There, we found that that quad-core processors do hold some promise, given the right software, and that Intel's quad-core offering is more attractive for power and performance than AMD's Quad FX.
Due to its relatively low clock speed, the Q6600 will perform similarly to a mid-range Core 2 Duo CPU in single- and dual-threaded apps. And, of course, it will offer somewhat lower performance than the QX6700 due its 266MHz lower clock frequency. Damage Labs is locked into GPU-testing mode right now, so we don't have any performance results for the Q6600 yet, but we'll see about rectifying that before too long.