Can I do this with Rekordbox dj?

Can I do this with Rekordbox dj?

Hi, I have a local DJ store that is offering me a DDJ 400 for 229.
I want to get it , however , for at home, I still would like to external mix on my Numark M6 , connected to a ESI UDJ6 audio interface, which is routed to 3 decks of Traktor atm… I want to route this current audio setup to rekordbox and just use the midi portion of the DDJ 400 in Rekordboxdj.
My controllers are Behringer Cmd PLl1s. I wish to swap the Behringer for DDJ.
For on the go, i will use Rekordbox and DDJ. No mixer.
My ultimate goal is to phase out Traktor as it just feels dated to me.

Or should I just go with my first thought and get an XDJ RR with my tax refund?

I think it’s possible, just a matter of selecting a different audio output with both the interface and controller selected. Doesn’t matter if the software has external mixing mode or not. But to be honest, it’s been a year or so since I played with RbDJ, don’t remember all the options in the software.

Only Serato doesn’t have that capability because of need to recognise the audio interface it’s using as certified.