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?
thosb
I owned a pair of 2.3's some years back and I think your problem is the VK-55. I had a pair of modified Threshold T-50's (converted to mono blocks). They were owned by a former employee at Threshold where they did the modification and my 2.3's came to life. High current solid state is the way to go w/2.3's. I was using is w/a Audio Research SP-16.
Agree that high power ss amps are the standard choice for Thiels in general, and the 2.3s impedance curve does NOT make them an exception.  However, the BAT VK-55 sounds much better than my previous amp (Krell KAV 300-iL, 200 wpc at 8 ohm, doubling down to 4 ohm), maybe it's just the sound of tubes that I am enjoying? BAT literature suggests this amp should be capable of handling challenging loads - there's even a 2 ohm tap - that being said, I know I can do better amp wise.  But to keep the sound of tubes and switch to high current ss amp means I need a tube pre-amp, and now I am right back where I started!?! 
I'm afraid a real change in sound or dynamics demands other speakers. All the others are just adjustments to the existing sound. Thiel is a really fine speaker and I owe them a lot (still got several) but they are not the last word in anything. YMHO.
Recently I was not pleased w/my sound. Same problem music was flat at the top end. Just lacked dynamics sound was flat. My amp in my case wasn't the problem. A Bryston 2.5 SST2. It was the tube preamp. A CJ ET3 SE. Sold it for a Luxman CL 38 U-SE more on the neutral side and the whole system just kicked in. In your case maybe a Bryston preamp might be the ticket. I think an all BAT system will really kill the top end of your 2.3's. All BAT to much warmth.
The actual answer is in the listening. No theory is going to replace actually LISTENING to whatever gizmo or notion you have hooked up. Sure you can argue theories all day.. But the answer is in only one place. YOUR EARS, listening to whatever.
I own several preamps. and regularly use more than one at the same time. So I can say I am ANTI-(add whatever fancies you). yeah they become ’tone controls’. Why would I care what somebody else calls it? the sound is all I care about. Right now I have my $40 used disc changer to my $7000 SACD player as DAC, to the Threshold FET10 line level, to the Conrad Johnson ACT2, to the Bryston BP-26 (which has the only XLR line out to the amp) SOUNDS great. I can leave off the Conrad Johnson and lose little, but it just has that last extra bit of greatness WITH it in.(probably second harmonics added)