Don't bother. Any stand alone DAC you add will be a lateral move. Or worse you will lengthen the signal path allocating money for a cable for no reason. If your preamp were purely analog then yes. But you have one of the best onboard already.
DAC options to consider for Innuos streamer
I currently listen to music through Qobuz with an Innuos Zen Mini Mk III as a server and Roon core. Rather than the Mini DAC I use the DA2 DAC module in my McIntosh MA8950 integrated amp. My speakers are Sonus faber Olympica Nova IIIs. I enjoy the sound quality of this system.
When I upgrade my streamer to an Innuos Pulsar, what DACs might I consider that would be an upgrade from the DA2 module and would complement my system?