I took a stereo test tone at odb generated on the mac using a freeware app from versiontracker called make a test tone. I used a stereo file becuase reason only outputs stereo files so i decided to use a stereo file.
I had an nt-xx going straight to the hardware outputs and tried a few different settings.
i was not able to generate a sound file that was the exact same amplitude. the output was either much lower or it distorted...not clipped. Ivthink that you (robin) should download the testtone and do some experiments and see what you can find. the link below will take you to a web page that has the file: testtone 1000hz etc.zip let us know what you find.