Is no preamp really better that a good preamp?

That's so the missus doesn't leave fingerprints after she's stabbed you in the back.

Here’s another incident

A women is on trial for murdering her husband by bludgeoning him to death with his antique guitar collection

Upon taking the witness stand the judge asked her ... “So first offender” ... to which she replied “No your honor , first the Gibson and then the Fender”
.

There might be more to the "impedance matching" than is obvious. A lot of amps have a DC block capacitor at their input, which attenuates low frequencies with a starting frequency that varies inversely with the driving impedance. IOW, with a high driving impedance, the blocking capacitor lets more ultra-low stuff through (which might be good or bad depending.... some amps and speakers need to keep that stuff out).
I use a series cap as a first-order highpass filter to cross to a sub, and a 'passive' box would move the crossover point all over the place.

I am at RMAF and saw the bespoke passive preamp that George posted the link to. It is quite a piece of art, has very smooth input selection and 47 step volume control, and both balanced and RCA connections. Unfortunately cannot judge the sound because it was only on a table display. Based on the view under the hood I can say it is well manufactured with proprietary wound transformers but at the price point it sure makes me pleased I own high value passives like the Lightspeed and Slagle AVC.

Interestingly, Paul McGowan, designer/manufacturer of the OP's DAC, has just in the past few days been posting thoughts on the very question being discussed here in his blog at the PS Audio site. Some excerpts:

My adamant stance against inserting a preamp between a high quality DAC like DirectStream and the power amplifier should be no surprise to readers of this blog. As well, my subsequent turn around embracing the exact opposite should lift no eyebrows either. But why would inserting an extra piece of gear in the signal path sound better than a more direct approach? How could this make sense? ....

... For a long time I found that DACs with no-loss digital volume controls sounded better, cleaner, livelier, directly into the power amplifier. Whenever I inserted a preamplifier it sounded different–but not better. That is until I tried a different preamp. My first revelation happened with the stunning Aesthetix Calypso preamplifier. Placed between the DAC and power amplifier, music took on a life and dimensionality that took all of 10 seconds to find it was better–not just different....

... I had written earlier that it’s likely I am asking the wrong question. How could adding more to the signal path make the system sound better, not worse? It turns out the logic is correct: it cannot. So why does sometimes adding a preamp between a DAC and power amp help the system sound better?

Because it’s helping the DAC not sound worse. And that bit of logic is key to answering the question....

... Imagine we have a DAC with an identical output circuit to that of a preamplifier. How would this respond driving a power amplifier directly? Theoretically as well as a preamp and, perhaps, better because we haven’t another component in the mix. But here’s something you may not have thought about.

DACs are significantly more sensitive to power supply changes and noises than preamps. When an output stage struggles to drive a complex load, it is the power supply feeding its output stage that sees these changes. If this occurs in a preamp, it has little effect. But that same situation, when applied to a DAC, has very different results indeed. Small changes in power supplies have big impacts on sound quality–especially jitter.

So this is one reason, and there are more, some preamps can help a DAC.

Makes sense to me. So if Paul McGowan can do an about face on this issue, at least under some circumstances, I guess I can too :-) But I believe that in general the opinion I expressed in my first post in this thread still stands:

09-23-15: Almarg
The burden of proof should always be on adding anything to the signal path that is not an obvious necessity. In this specific case a preamp is not an obvious necessity, and per George's analysis (with which I agree) the odds appear to be in favor of that burden not being met. However, as others have indicated the only way to know for sure is to try it.

Regards,
-- Al

I'll go along with that also Al,

1: The dac's power supply for the output stage as PM states is not up to it.

2: If the dac output buffer is not low output impedance <300ohms, as some very weak tube output dac are today some I've seen up to 3000ohms.

3: The impedance load as seen by the dac output is so severe that only something like a Krell preamp's output stage at 1ohm output impedance is able to drive it.

Cheers George