The Best Preamp is no Preamp?

Brandonhifi the Qutest is not designed to drive an amp directly. There if this is your intent  I would look at the Hugo2 at a minimum as it has some form of volume control. The TT2 and Dave a designed with this use in mind. For my money the best implementation of a dac as a preamp is by MSB but you are talking about a lot more money to get into one of their dacs. 

The best preamp is no preamp only until you hear high quality active preamp. The added resolution, transparency one may hear sans pre vs lower quality pre is generally initial novelty Many will discern analytical flavor over longer term, seek out pre to add, others may assume this as good as it gets, until they hear the magic that great active pre can bring to the table. I can easily convince myself my active pre is most important component in my system, it was game changer for me.

Streaming directly to my power amp on my second system for years. In my First Second System, I had an amplifier with gain controls and a Denon CD player that also provided some limited volume control. Plugged the CD player in direct to the power amp. Great sonic result and it’s simpler to manage. Even simpler now with streaming. 
 

Since the OP mentioned a Marantz preamp, will also say that I’m very happy with the sound of my main rig setting my AV7001 in PureDirect mode. I need a preamp on my main rig because of all the input devices to control.  But it just seems to make sense that if I can cut out a layer of electronics, I’ll get closer to the actual source signal. This seems analogous to hearing a Direct-To-Disk vinyl record vs ones that were made mixed and mastered the usual way. 

Sound reinforcement systems don't have pre-speaker-amp "preamps" as a concept even.

Of course they do! The preamp is known as a 'mixer'.

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There are four functions a preamp provides:

1) provide input switching

2) provide volume control

3) provide any needed gain (tuners usually do not make enough output to drive a power amp directly; many make only 1 volt)

4) (and the least understood) control interconnect cables; prevent or reduce them from adding colorations due to cable construction (if you've ever auditioned cables and heard differences you know what I'm talking about).

If you use the balanced line system, you can reduce cable artifacts and should eliminate ground loops entirely. The balanced line system is intended to be low impedance which rules out passive systems. I tried this decades ago and found dramatic differences between cables that were eliminated when I used an active line stage that drove balanced cables properly (e.i. supports AES48, the balanced line standard).

There are a lot of debats on this but I just share my experience.  Shorter signal path is better. I am running straight from Dac (as Dac mode) to PA and the system sounds really well.  I maximize the volume on the source and adjust the volume on PA to reach the listening level.  I also found playing CD/SACD player straight into PA is better than going through Dac, even though the internal Dac inside the player is lesser than the external Dac I had.