If you're trying to do an overall performance test, CPU speed (or "power") is only one factor. If your task is I/O bound it may even be a negligible factor.
In general, trying to scale performance numbers is difficult. You may want to try running some baseline tests a few times on each platform to see if the results are comparable. If so, you could then proceed with testing on your machine and scaling the results up or down. It's not perfect, but it's probably reasonable.
You can use Perl tools like Benchmark.pm for conducting the tests, but the problem itself is much broader.