Upgrade DAC Power Supply, Streamer, or ?

This is a bit long but I wanted to give as much info as possible. My current system: Van Alstine SET 400 amp, Van Alstine T-10 RB tube pre-amp, Denon HEOS 2 streamer, Merason Frerot DAC with factory wal-wort power supply, Salk HT2-TL tower speakers.  I would say this system is slightly warm of neutral, open and detailed. I enjoy listening for long sessions with no fatigue. I've been streaming through Tidal for a year and rarely play CDs or Vinyl anymore.

The external Merason DAC was the most recent addition and works well with the Denon streamer bypassing its internal DAC by using a coaxial cable. It was a noticeable improvement vs. the Denon's internal DAC. 

The Denon HEOS 2 was my entry-level streamer and it does sound good. The only thing I have to compare to is my Wiim Ultra which is also a fine unit with good SQ and features.  The external Merason DAC was a noticeable improvement to both streamers.

Innuos Zen Mini Mk 3 with the Innuos LPS are a reasonable price on the used market and praised for sound quality and also for the SENSE App.  It would also allow me to put my aprox. 1300 CDs on the internal SSD and help with physical down-sizing. I'm not sure if the internal DAC of the Zen is as good or better than the Frerot, but it appears I could bypass the internal DAC using the coax. output.

So which would give me the most bang for the buck by upgrading; the Frerot power supply, or streamer to the Zen Mk 3 ?  I am MAC based and technology is not my forte.  Budget is $2000 or less.  Thoughts and recommendations are appreciated.  Thank you.