I recently purchased an Aavik U-300 to achieve an all Borrensen designed system (Raidho D1.1 speakers, Ansuz cabling, Ansuz Darkz resonance control and Ansuz mainz8 Diamond power conditioning). I previously used 2 Devialet Expert 200’s in a mono configuration with a variety of cabling and the Raidho D1.1’s
For me, there was a noticeable sound upgrade in changing all my cabling to Ansuz. I noticed an immediate improvement in clarity, dynamics and realism.
in going to the U-300 from the Devialets it was more subtle. I did not find that the Aavik improved midrange (at least, not the way a tube pre or amp brings on that lush sounding euphonic). It did however slightly improve the full sonic signature but not just one aspect (bass, treble, midrange, etc). Also, I found with the U-300 I needed to do some speaker repositioning to get the best sound. Initially, with the speakers in the same position as with the Devialet the sound was flat, one dimensional and uninviting. I was disappointed, to say the least!
But after multiple subtle speaker adjustments, I think I dialed in the U-300 and the Raidhos to achieve very enjoyable and lifelike result.
So, bottom line, the U-300 did not impact the midrange directly (for me) over the Devialets but did achieve a more lifelike sound after some speaker adjustment.
Hope this helps (a little)