How important is a preamp for purely digital sources?

There is another aspect to this entire discussion that has not been touched upon. While a preamp may be technically perfect and not enhance or degrade the sound there are two more links added to the chain with an external preamp that need to be considered. The interconnects. I have yet to find an IC at any price point that does not "color" the sound or add noise. I'm a firm believer in the concept of less (quantity not quality)  is more when it comes to ICs. 

I know that but integrateds were not the subject of this discussion. preamp (s) are. When considering how important a preamp is (subject of discussion) and its effects on digital sources one must not forget the IC part of the equation. Years ago I added a very pricey and highly regarded BAT VK51SE to my then all digital system. I had used a pair of highly rated mid/high-line Audioquest ICs that I had from a prior system. The results were not as expected. The sound lacked warmth and was slightly muddy; that is until I replaced the ICs with Synergistic Resolution Reference Active series IC’s. The difference was astonishing; the expected tube warmth was now there and the muddiness was gone. This experience leads me to wonder if the results that some posters are touting are really the result of the preamp addition of the effects of the additional ICs.