With your logic, a Yugo with a supercharger is faster than a Enzo Ferrari.
Sandy Bridge = poor man's i7.
Let us compare the i7-2600k with any non Hexacore i7, as they fall under similar price ranges.
The i7-2600k is faster clock for clock, starts with a faster clock speed, overclocks better and has far better memory throughput.
They both have the same number of cores and are both hyperthreaded.
In performance benchmarks released thus far, there is no doubt that Sandy Bridge outperforms quad core Nehalems.
On a side note, if you are building a new rig, SB will come out slightly cheaper, given current pricing.