Quartus Performance - What Processor, Memory, Disk?

For operating system, it doesn't matter much for Quartus - Windows and Linux have similar compile times.

Bigger caches definitely help a lot.

One thing to keep in mind when you are benchmarking multi-core compilation: Quartus is parallelizing the time-intensive algorithms, but not as much for the constant overhead of a compile. If you benchmark a short compile (eg. 5 or 10 minutes), you won't see much parallel benefit since those 5 or 10 minutes are dominated by constant overhead.

On average, we measure ~20% compile time reduction when using a multi-core machine - your exact performance will depend on your design. For example, if your design is hard to route, it will spend more time in the algorithms and so parallel will be more important.