Well Artmindes, Number one, Im not a headphone listener so can give no insight on differences between that and listening through speakers. Actually Kbarkamian's observation concerning the Rega would parallel mine comparing the Havana to other ultimately more resolving budget digital components I have heard and have on hand. No, the Havana is not the last word concerning detail, soundstage width and frequency extension. This became totally apparent after I acquired an Oppo 95 although I prefer the Havana on most music. On much of the music, small scale in particular the Havana is superb with great timing and, tonality. The issue again with the Havana as stated above really shows its limitations on large scale dynamic recordings. What it amounts to is that on some recordings I would prefer to listen to the Havana on others the Minimax a recent acquisition and does provide the things that were missing in the Havana yet more refined and engaging than the Oppo. The Oppo is on transport duty. Another plus which I personally like is that BOTH Havana and Minimax have tube outputs which permits me to tailor the sound to my tastes and system. I'm not really into op-amp output stages which the Minimax has as a standard option, trying to be all things to everyone I suppose. I can get more variation from different tubes.
Now to put all this in its proper perspective many things must be weighed. Since you are listening to headphones only it would seem to me that the Havana or Rega would meet most of your criteria based on your primary listening preferences and for use as a headphone exclusive DAC. Your friends comment concerning a grayish color when listening through speakers is not totally clear to me as to what he means, as in opaque maybe? By that I mean lacking in transparency or resolution but on the plus side, a richer sound. I dont know his speakers or system but would say that the NOS Havana is definitely not the last word again, in transparency, yet it would be sufficient for many listeners, others will want more. I personally want BOTH! This is why it is difficult for me to give a concise answer. I have a system that has basically stayed the same minus the constant tweeking and discovering quite recently the quantum improvements in budget digital products, a real eye opener. My preferences in listening are towards accurate and transparent to the extent that any system is either. Then again there are budget considerations which makes putting together a musically satisfying system which realizes our or at least my personal goals all the more satisfying and rewarding. If it means anything I will say only this, I AM NOT prepared to sell my Havana anytime in the foreseeable future.