The problem I have with the CT4150 is the specifications for the gain. If you look at the cut sheet, it is 25 dB, In the manual, page 51, it is 26 dB, and on the website home page, it says 27 dB.
If we assume the gain is 25 dB, then 1.4 V will drive it to output 77.5 W 8 ohms.
assume 26 dB, it will be 97.54 W 8 ohms.
assume 27 dB, it will output 122.8 W 8 ohms.
So the 1.4 V sensitivity will only work out if the gain is 27 dB, I have no idea why they specify 25 dB and 26 dB in different places.
If you want to assume the worse case, then it would be 25 dB gain, and in that case you will need about 1.78 V to drive the amp to its rated output of 125 W 8 ohms.
The Denon pre out can output up to 4 V or a little more before clipping, so no you don't need to ask yourself any questions, not technical questions anyway.