The stock WinRAR results were quite good, and the overclocked ones were even better.
WinRAR Multi-Threaded
Here we see that the multi-threaded WinRAR can actually make good use of four cores - so it does not suffer from the self-imposed "two thread" limit of most other "multi-threaded" benchmarks.
The quad core QX6700 dominates, followed by the overclocked E6750.