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'm about to pull the trigger on the Benchmark HPA4 as a linestage and let it do the volume control that has been done by my Benchmark DAC2 HGC, which is feeding a VAC 200iq amp into Sonist speakers.  The system currently sounds great, but most all reports on the HPA4 say it's a definite step up from the HGC in the DAC.  I seem to have a weakness for odd products that claim some special quality, and I find myself curious about the new Linear Tube Audio MicroZOTL preamps.  Anyone want to talk me out of the HPA4 and into the ZOTL?  I suppose I could order both and return the lesser, but I hate returning stuff. Thanks.
I have been told for over  2 decades that the shortest path is the best. So I have been going direct from my MSB Platinum DAC III with passive volume control into my amp. 

I recently added a Backert Labs Rhumba 3 Extreme to my system. The difference the Rhumba has made was dramatic. It was like the curtains got pull back and I was hearing the music for the first time. Everything just sounded clearer; especially with low level details. Sound stage improved along with over all musical texture. Every note was conveyed with a sense of presence,  especially with female vocals and string instruments. And the decay just goes on forever. 

The Rhumba 3 Extreme has been the single best addition to my system in over 12 years.