What will a preamp do for me?


Missing in the chain below is a preamp - I use the DAC to control volume.  This is my only source and will be for some time.  What could I gain by adding a preamp?

I have Thiel CS 2.3s driven by a BAT VK-55, sourced by PS Audio PW DAC, with bridge II, mostly tidal.  The DAC serves as a preamp in terms of volume control.  Mostly Audioquest cables, amp power cord is Cardas Clear m, all fed by PS Audio upc-200.

I am am hoping to improve the highs, which sometimes sound smeared, too much sibilance; would like more air and clarity.  Loud rock sounds flatter, less dynamic than I’d like.  I am not willing to give up the deep detailed and beautifully resonant mids.  Willing to spend up to $3000, used is ok.  Totally balanced is a must.  Not currently willing to entertain the idea of different speakers - my goal is to make the 2.3s sound as good as reasonably possible before moving on to other speakers.  It’s easy to find a really good preamp in this price range, so much so I am almost paralyzed by the choices.  Aesthetix , Ayre, ARC, several BAT, Parasound and more all have apparently excellent models in my price range.  Patience would put Atma-sphere and PS Audio within reach.  Which is best for my situation?  There’s no way to audition all of these, how could I avoid getting on a preamp merry-go-round?  Or should I spend my money elsewhere?
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I'd say be patient and get a Atma-Sphere MP-3.  Very accommodating  to for rolling tubes - you can tailor your sound to anything you like.
You might have to stretch your budget a wee bit for a used one, but you'd be happy if you did.
"Count me in the crowd that likes to color the sound."

Ditto but I disagree with the general premise that direct even without bit stripping is the way to get the most "transparent and dynamic" way to get the source to the power amp. The outcome is completely system/component dependent. Also, in most DACs with a (digital) volume control, the bit stripping typically occurs at very low listening levels. 
Well the right preamplifier should increase the size of the sound stage making it more expansive creating a bigger sound. deHavilland uses big tubes in their preamplifiers which do just that. Many tube pre's use smaller little tubes, partially so they can put a cage over the top for cosmetic reasons. 
They will customize the pre so it will match the input levels for peak performance. Take a look.
Could you bring your DAC over to a friend who has a preamp, to see if running your DAC at full volume eliminates the issues you hear at home, but running it below full volume adds it back in? That seems like a reasonable way to test if the volume control is having an impact on the sound quality.

Different preamps will have different impacts on the sound character when added to an existing audio chain.