I’m looking for an sleek integrated amp under $15k

The two best integrated amps I've heard at that general price point are the: Audionet Watt ($18,800) and the Mola Mola Kula ($15,055).  Honestly, nothing touches them sonically!  Since you specified $15K and below let me focus on the Mola Mola Kula.  Very transparent, 3D, dynamic, and has great bass.  For extra, you can also add a world class DAC (same as the famous Tambaqui) as well as a phono stage (same as Lupe), built-in, if you choose.

The current crop of Mola Mola amplifiers are not old technology.  They represent up to five generations beyond even the NCore module. The outlying circuitry is also unique to Mola Mola. Regardless of class of operation, they sound fantastic!