It all depends on what you are trying to do exactly. As an example, I use the pre-amp outputs from my Schiit Audio Vali 2 to run a Sonance ASAP1 driving my Energy bookshelf speakers and a Velodyne sub though a solid splitter. It works fantastic. I get the clarity and warmth that I love about tubes, and it comes through extremely clear. However, it should not be interpreted that this in any way will equal a fully dedicated hi-end pre-amp designed for that specific use rather than that of a headphone amplifier 1st, with a secondary thought of adding pre-amp line outputs. I suspect this will sound about as good as you could expect from a dedicated pre-amp around the $500 range though, and unless you are expecting this thing to sing so well with your system that unicorns will flock to your home for a listen, then you will be very satisfied. It will also sound better than the pre-amplification that you get out of most home audio receivers under $1k. I haven't had a chance to put this into the Outlaw amp that I have powering my home system with Golden Ear Titan II's which with their 1200watt sub amps in each speaker should sound superior to the Denon pre-amp outs on my receiver, specifically in the separation, soundstage, and headroom department. The Denon is no slouch, but they also didn't put as good a pre-amp in it as you will be getting from this DarkVoice.
When I first got my Schiit stack (Modi Multibit and Vali2) I hooked them up through the pre-outs to the Bose companion speakers that I had used as my desktop set up for a few years. Immediately the difference was apparent. I was able to raise the volume knob on the Bose speakers to 11 (well, I wish all volume knobs went to 11 out of respect to Spinal Tap) , and even putting the speaker straight to my ear, it was absolutely quiet connected to the pre-outs on the Vali, no buzz, hiss....nothing. Then when I started to play the music though them, it made them sound like they were easily ten times as good as they had been with the internal pre-amp off of the crap computer 3.5 output jack. I was shocked to hear actual imaging coming out of my little Bose. I don't even like Bose speakers honestly. I just bought the Bose because they were on sale and decent enough for my desktop at work for the time being. Back in the 80's we used to say "no highs, no lows.....they must be Bose!"). Either way, it was enough for me to grab my Sonance solid state amp not being used to push some Energy speakers, and also purchase a Gemtune APPJ PA1501A to run my old but outstanding Paradigm monitors at my desk. The Bose speakers are now on my wife's desk. :)
As far as the DarkVoice goes, I'm considering picking up one on this drop too since it will do about the same thing as my Vali 2, but I also expect it to sound better with some of my cans, and since it also has the pre-outs that you are mentioning using, I want a second amp source for my Massdrop Sennheiser HD6xx's and HD600's, AKG K7xx and Nobel IEMs and a handful of other IEMs that I think will sound great with it along with being able to drive my amplifiers. Also hoping to get a Jotunhiem for X-mass which would be fun to listen as a DAC through this as well.