Think of it this way: save for a small handful of highly threaded and/or extremely memory bandwidth sensitive applications, both the 2500k and 2600k are already faster (in 98% of assorted benchmarks) than the i7-950, i7-980x, and the 990x.
Unless your profitablilty is riding on the perhaps two applications that Bloomfield/X58 excels at with a 2% lead, there is little reason for considering it over the better performing Sandybridge rigs..