I have a Cambridge Audio Azur 740c, which as a DAC sounded more or less at the same level as a DAC1. I've had goodness knows how many hours/days/months with a X-03SE and while the Esoteric is most definitely better, the difference is not as massive as the price difference suggests. Quite honestly, I think you're looking at spending a huge chunk if you want any night and day increase in sound quality.
I have very limited experience with the Chord DAC64 used with the Blu transport. It's pretty darn good, but will set you back a few times the cost of a DAC1.
What's your target price range anyway? There are quite a few top-notch CD/SACD spinners that have DAC functions as well: dCS, Meridian, Resolution Audio, APL HiFi, etc... Have you considered upgrading your SA60 to one of them?