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

You should be able to get a Gryphon Diablo 300 with DAC option at $15k as the new 333 is out (or coming soon).  It is one of the best integrated amp at this price - lotsa power.  It will blow away the Naim. What speakers do you have?

McIntosh MA12000.

I have a Lyngdorf Processor. Absolutely love it. Sounds incredible with great workmanship. My votes for them. Good Luck and Happy Hunting  

I have never heard an integrated amp over 5K and probably never will. Based on reviews, I'd want to hear a Simaudio model for sure. 

I would never look for one with a phono input but a separate phono preamp.

How about this Aavik Acoustic U-300 listed here?

https://www.audiogon.com/listings/lisb7hh8-aavik-acoustics-u-300-solid-state