You should test with different applications to properly ascertain how stable the CPU is, particularly as you approach what you think will be your final clock speed. LINPACK-based applications like IBT/LinX are useful but not necessarily the ultimate determinant of stability, especially since they don't produce a constant load on the CPU (which is also why they are useless for temperature testing).
They don't produce a completely consistent load, but the load they do produce is consistently higher than the load of something like Prime95, which is why they are a more difficult stability test to pass than Prime. In general, if a computer is Linpack stable, it's stable under pretty much everything, though there are a few odd cases every now and then. They also give the highest temps of anything I've tried on my i7.