I would certainly concur with Gonk on this issue, however, I might offer in addition to the internal test-tones of your Pre-Pro, you strongly consider along with the SPL meter, as a further option, using the test tones from an external disc played on your BR/DVD player to measure speaker levels as well. I have found that on occasion that in some products, the volume levels of certain channels may differ between the internal tones of the AVR/Pre-Pro and those from the test disc and if you are one that watches a considerable number of movies on your system, the levels from your player will give you somewhat of a more accurate picture as to the appropriate sound levels of the various channels coming from the movie that are being fed to your amps and ultimately the speakers.

Of course, in the end, if you find in comparing the test tone levels from the disc and the Pre-Pro that they match anyway, then it won't be an issue.