Do Audiophiles usually keep the gain of the digital source at around 80%?

You don’t necessarily need a preamp, and I don’t wish to be contentious on this subject. However, a DAC with a well-designed gain stage—like the discrete Class A output stage in Harmony Micro DAC—can drive an amplifier beautifully. I used to be in the preamp camp for a while, but after getting a quality DAC like this, I’m switching back to the “no preamp is the best preamp” camp.

Inserting a good preamp in the chain can often sweeten the sound and augment the soundstage, but I also notice a slight loss in dynamics. I have actually mitigated that through the source by adding a DDC and good cabling. I believe the source dominates the quality of the signal chain, rather than the backend. This may contradict your statement, but I am simply sharing my experience.

Obviously the A8 has analog outputs because it's a dac/streamer, the volume control is in digital realm, it does NOT function as a pre.

The generalization of pre's as superfluous because it simply adds distortion, reduces dynamics, sweetens sound is absolutely ridiculous. I'm sure there are many here with quality preamps that find them indispensable. 

@lanx0003 

One thing we can agree on, I think, is that whether standalone or integrated to an amp or to a DAC, a preamp or preamp stage is always involved.

Sound quality notwithstanding, I have analog sources I need to switch, and I prefer discrete components performing single functions in my system; and finally, with very few exceptions, the best preamps are separates.

So, while a separate preamp makes the most sense for my own use case, that’s all preferences and there is no right or wrong answer.

Now I am sure some DACs are equipped with decent preamp stages, and I certainly don’t know every one of them, but I am going to have difficulty accepting that the vast majority of them are in the same league as high-end separates.

Finally, at the risk of being labeled a VC snob, I am going to have to respectfully push back against the notion that a digital volume control, even a 32-bit one, is an acceptable choice in any but value-conscious devices. Neither is a $15 Blue Velvet, by the way, despite the fact that those are original equipment in so many almost-high-end preamps selling for $2000 or $3000 or even more 

@sns  DMP-A8 features an R2R (resistor-to-resistor) volume control. This R2R (Resistor to Resistor) network, implemented with precision resistors and relays, is part of the DMP-A8’s fully balanced analog preamplifier section.  This says in the manual.  Where did you see that its volume control is in digital domain?  Did you actually own A8?

@devinplombier One thing we can agree on, I think, is that whether standalone or integrated to an amp or to a DAC, a preamp or preamp stage is always involved.

The quality 'gain' stage (or buffer) in Harmony micro Dac I was referring to earlier is NOT a preamp section, rather a 'voltage' gain stage serving two purposes: increase of voltage to line level and impedance matching.  It does not have the volume control to be qualified as a preamp section.  However, it drives my amp pretty well.  The 32bit digital volume control from Wiim Ultra renders no resolution loss, transparent sounding even down to low level.

at the risk of being labeled a VC snob, I am going to have to respectfully push back against the notion that a digital volume control, even a 32-bit one, is an acceptable choice in any but value-conscious devices.

I wouldn't call it snobbery, but there's definitely prejudice involved. I did a simple comparison between the digital volume control on the WiiM Ultra and the 64-step relay analog volume control on the highly praised Schiit Saga 2. At normal listening levels (60–65 dBA), the sound quality was nearly indistinguishable—both were detailed and transparent. However, at lower volumes around 45 dBA, I actually preferred the digital volume control. It delivered articulate bass and clear treble, while the analog counterpart sounded a bit muddy. You might argue that the Saga 2 is only mid-end and that a high-end preamp would perform better. But that’s precisely the point of this comparison: I was able to get better sound at low volume from a device like the WiiM Ultra, which is priced similarly to the budget-friendly Saga 2—whereas achieving the same low-volume performance with an analog preamp might require spending significantly more ($$ or even $$$).  Note that the soundstage shrinks in both scenarios—there's no clear winner in either case.