You can make as many hardware changes as you want before activating your license.It will not affect the functionality or the activation state of the software.
After activation, you must reactivate QuarkXPress if you make a significant hardware change (such as changing the Ethernet address on a Mac® or changing the computer processor) or if the activation mechanism is damaged in some way.
Note: If you plan to make significant hardware changes to your computer, you might want to use the License Transfer feature to deactivate QuarkXPress first and then reactivate it on the same computer after you make the hardware changes.