Why is it then that Marantz on the website publishes the voltage of the preamp as 1.4v? I was worried I would not be able to use all of the amplification this way.
I don't remember seeing 1.4 V on Marantz website, if you read the manual, it says Analog: 1.2 V, D/A output: 2 V at 0 dB playback. That's very vague as it does not really say much about the load condition. Even the 2 V at 0 dB playback mean little, because it does not say what is being playback, it most likely mean input signal at 0dB FS level, as that would be consistent with the ASR measurements. The Analog: 1.2 V spec is almost useless, because it says nothing about any load, and/or input conditions at all. I can take an educated guess, but it would still be just a guess. Again, its like their power consumption specs, it says 710 W, but anyone will know for an AVR, power consumption depends on how/what it is used for/with. We can also guess the conditions under which it would consume 710 W, as Gene did say something about Sound United follows IEC 62368-1 for such ratings. You didn't ask about this one, but I am using it just as another example about how vague manufacturers are, about those audio specifications. You can try asking customer support, but from my experience, unless you insists on them getting an answer from their engineering/design team (they did for me once or twice but that's it), they usually would just regurgitate what their website info says, and that you already know anyway, so no help there, usually, if the info gets just a little more technical.
Bottom line: specifications such as pre out rated output, power amp rated output, power consumptions, and many more, are often quoted for under specific load conditions that they don't always tell you. So you have to seek out the information, such as from service manuals, their own training videos (such as Masimo') and bench test results, if you want, or need more specific information. In the case, we are fortunate, as thanks to ASR, we do have bench measurements, and also a Youtube video by Marantz/Masimo.
You can also reference service manuals, though in this case you won't find one for the Cinema series, but you can find it for the earlier models. I am quite sure any of those AVRs can drive your power amp to their full rated output without any issue.
In fact, in one of my 2 channel systems, I am using an <$600 AVR-X1800H to drive my buckeyamp's Hypex based power amp, the NC502MP that has only 25.5 dB of gain and is rated 300 W 8 ohms, 500 W 4 ohms, no issue whatsoever. So, just relax and enjoy your Cinema 40, that seems like an excellent AVR.
From Owner's manual:
By the way, Onkyo, Yamaha etc., even the $6,900 Arcam don't seem to do better, here's what you get for the $6,900 Arcam AVR31:
Yamaha, like Onkyo irrc, used to just say 1 V, like Arcam.., but in recent year Yamaha also provide a second spec, one that described as "Maximum", so you will see the following in the manual of the RX-A8A:
