DAC with the best midrange ever.....

The Manley Reference DAC from the mid-late 1990s. Check it out here. I have had one for several years and would not let it go because it does the middle 6 or so octaves like nothing else. And with the help of Steve Huntley at GNSC to update power supply caps and a few audio stage caps, this unit was taken to yet another level of performance, particularly greater extension on the top to allow those magical midrange harmonics to decay even longer. No other DAC that I have tried renders the piano like this. The all maxed-out APL Denon 3910 that I also own has a little more low-level detail and a little more dynamic punch in the lowest octave, and it is quite musical with the 7062/12BH7A tube, but the Manley continues to be the midrange king.

Lots of good comments here. From the Krell products I have heard, the sound has always been rather sterile, dimensionally flat, but very resolving. I can say the same about Ayre, Spectral, Levinson(Madrigal), Klyne, etc.

I have heard some of Rapogee's digital gear in my system. The Audio Aero Capitole was actually quite impressive. If you don't hear midrange magic here, you need to focus on other links in your system.

A tube amp is not going to affect the performance you seek anywhere near to the same level as a tube line stage. I have been through many tube line/phono stages and amps, and time after time, the tube line stage is the make or break link in the system when it comes to capturing midrange textures, harmonic overtones, ambiance, etc. Drop in a tube line stage preferably one with a tube power supply and compare to the Ayre and you will never go back. And then compare the Audio Aero Capitole with your solid-state DACs to know how good the Audio Aero Capitole truly is.

The problem with changing the amp is that the amp/speaker selection always go hand in hand with each other. Other than impedance matching between line stage and amp, your options on line stages will be far greater.

Another super critical link here is the IC from line stage to amp. Try to audition the Jade Audio Hybrid, Stealth Indra, Purist Dominus to get a feel for how significant these cables in this link can affect the sonic attributes I mentioned above.

I would suggest you hunt down or borrow line stages from Aesthetix, VAC, and BAT as a staring point to get a feeling as to what you are missing here. The Audio Research Reference 1 and 2 line stages do not compete here. As much as you might be a Krell and Ayre fan, these product lines do not excel in the areas for which you seek now. Until you address this, not even the power of the magical DAC from heaven has a chance of shining through.