Preamp or DAC

I’d start with the preamp for the biggest absolute level of improvement, and the Spatial Audio Raven (Sachs/Olson design), Aric Motherload, and Backert Rhumba Extreme would all be great choices and believe all three offer a trial period, which is huge especially at this level.  Best of luck.

by the way could you tell me your favorite of the preamps you tried please. Thanks. Looks like Pass 12 maybe

Yes, correct, the Pass XP-12 is my favorite to date. I will stick with this one for awhile.

My recommendation would be to stay with the CODA preamp and upgrade the DAC. Your amplifier has 10k ohm input impedance which is pretty low. Tube preamps typically have high output impedance around 600ohm. Even though it meets the 1:10 ratio it is still quiet low as impedance fluctuates. It’s possible you will have a slight reduction in bass output. Trying a tube DAC into the 07 preamp will be no issues with the preamp’s 20k input impedance. 

Going preamp-less will present the same issue with a tube DAC direct into amp. 
Talk to CODA to confirm as I’m just speculating based on typical specs of tube preamps and DACs. 

You already have a top-flight DAC. The Coda pres are not nearly as good as their amps. As such, I think you’re better off going with a new preamp.

Thanks for all the feedback. You have given me a lot to think about. The impedance issue for sure I had not thought about yet. Generally, there seems to be a split decision on preamp first or Dac first. Honestly, when I asked the question I thought the answers would be Dac first but many feel preamp will make the most difference. But then I do need to look at possible impedance issues.