Not sure where you are right now or if you've made a decision, but I had my Krell 400xi running with a Benchmark DAC and Dynaudio Contour S3.4's a couple years ago. In my case, I found the lack of warmth to be the Benchmark DAC - I found it to be harsh and "in your face." I replaced it with the Electrocompaniet DAC and it's been a fantastic setup since. I also upgraded to the Dynaudio C1's and love the sound even more.
So, for warmth, my vote would go to re-evaluating your DAC situation, but I don't think that's what you want to hear :-)
So, for warmth, my vote would go to re-evaluating your DAC situation, but I don't think that's what you want to hear :-)