One DAC to Rule it All

I use the DBX DriveRack PA2 to control my subs.  In my opinion you are doing it wrong.  Take one output from your preamp and send it full range to your amp.  Take the second output from the preamp and send that to the DBX and use the software on that to set the crossover and levels etc. etc..  Run the subs with the crossover set to the maximum and set the level to approximate what you want but fine tune with the DBX.  The absolute last thing you want to do is have the DBX in between your preamp and your power amp.  The cheap DA/AD converters in it will destroy the quality of your sound but it is completely irrelevant for the subs.  If you don't have two outputs from your preamp I suppose you could always get a y-splitter.

You system is so convoluted that I'm not sure upgrading a DAC is going to make a difference. When it comes to the audio chain, simpler usually is better. I've heard this proven more than once.

I’m with @soix ​​​​@ozzy62 .  Why so involved?  Now, to play Devils Advocate, I doubt that anyone here has actually heard a setup like yours, and your ears are the ultimate judge, but the conversion back and forth would be enough to drive me nuts 

Convoluted? It's really nothing more than an active crossover (in digital form) splitting the signal between my mains and subs at 100Hz. I realize I could send the full range signal to my main speakers, and just use the DBX to the subs, but as I said I had done that for a long time and recently found that keeping the <100Hz from the main speakers gave me a nice increase in resolution. Other than going to a DEQX Premate to do all these features including the DAC from my server, I don't see any other way to get a 48db/oct. slope out to both the mains and subs for a reasonable cost. Also a 48 db/oct crossover in the analog world would be quite a complex and convoluted thing as well.

I also want to thank everyone for sending in their thoughts. I suppose dipping my toe into the digital realm more than once is considered blasphemy in home audio, but I am getting very enjoyable sound. I am considering the DEQX route as their internal AD/DA are of a higher quality. So even though I am seeking advice, you're all correct in the fact that I just have to try out all these configurations to see for myself. I will experiment and keep everyone apprised.