Best Preamp - NO preamp... (?)

Hi Ami, congratulations on a sound decision of running a high quality digital unit directly to your amplifier,  I've been doing this since 1996!,  of course this setup is opinionated, however,  those that believe going through another circuit board such as a active pre-amp likely does not have a truly balanced,  direct point to point wiring digital unit with a high quality volume control that has wide band specifications like 10htz to 60khtz or more,  this has extraordinary clarity and realism,  musicality, no color added that all preamplifier's  add! Cheers 

Some systems need help in getting the sound right . Speakers may be lacking in a department and the pre fills in the sonic virtue needed . Only way to tell is try . 

Hi Ami.
Since I have the same DS dac you have, perhaps I can shed some light.
First I have to give a dealer alert, since I sell the Ps line.
while the DS happens to have an extremely transparent volume, and it does sound great in my system, a top preamp will enhance your sound and enjoyment.
If one has a less than stellar pre amp, then yes the DS direct might in fact be preferable. But running the DS at less than full output (or with the -20db attenuator) is a compromise.
The preamp I’m running is a $15k all tube two box unit, but there is a stellar option at almost 1/3’rd the price.
Paul at Ps has stated that their new BHK preamp sounds much better than the DS direct.
In fact Bascom king has stated that it is the best preamp he has ever designed. And his other designs are super expensive. His hybrid design actually varies the level of tube gain as well as attenuate, so it’s a novel and very transparent approach.
While I haven’t gotten one in our system yet, having the BHK 300 Mono amps in our system, I can assure you that Bascom teamed up with Ps’s value driven aesthetic means these electronics, while not cheap, represent edge of the art sound at real world prices.
If you’re serious about building a world class system, (and you have an world class source in the DS- and one that keeps getting better with each new OS release) you need an active preamp (not a passive unit)
Also going balanced will help and means that even cheap cables can work extremely well.  
If you're ever in the NYC Area I can demo the DS direct vs. Through a great preamp.  Triode picture sound.  

It does, indeed, depend on each person's personal preference.

I have both and use both active and passive preamps, at various times, depending upon the sound I'm seeking.

I got a Creek OBH-21 Passive Preamp, primarily to use as a remote volume control.  And found the sound to be somewhat more transparent and somewhat more detailed and clear than my Parasound JC-2, and my Audio Research Ref 3.  Though, the "somewhat more" is a fairly small difference.  

I A:B'd the OBH-21 vs the Ref 3 with my wife as the judge... and... she clearly preferred the sound of the Ref 3 - called it more real and life-like sound than from the passive preamp.  Though, the passive preamp still sounded like it was a bit more detailed and clear.   

The tubes of the Ref 3, produce a deeper, more localized soundstage / image, which has more ambience - thus, the more life-like, realistic sound.  No doubt the effects of the harmonics of the tubes - "good distortion."  

The interesting thing is... the OBH-21 cost about $250, compared to the $4000-7000 of the active preamps to which I was comparing it.  So... for the money, it's hard to justify the price premium of the active preamps, when the passive preamp sounds so good and so close to the active preamps.  And... I understand... some of the custom made passives, sound even better, for a nominal increase in cost.

One compromise... might be... to use a passive preamp and a tube buffer - which might give you the best of both passive and active preamps.  

Of course... if you must have all of the connectivity and features of a better active preamp, then most passive preamps are not an option.  

So... "to each his own."