If we were to judge the Core 2 Extreme QX6700 only based on the two first SiSoft benchmarks, we could conclude prematurely it's a hell of a buy even at $1000, obviously there is more to it.
Although both the E6700 and QX6700 operate at 2.66GHz, the QX6700 has four cores working away while the E6700 has just two. The end result was 3.5x more performance for the QX6700 over the E6700, which is obviously very significant. Despite this, Super PI showed no performance gains for the QX6700, as this program does not support quad-core processors. PCmark2005 also showed no performance gains for the QX6700 over the dual-core processors.