I've only heard the un-modded standard Unico, but with some premium tube (don't recall which), and only in two very similar systems paired off with Solilquy 5.3 speakers (90db efficient floorstanders). In one room it sounded pretty compelling to me, in my own room not nearly as much so. I find the Panache far more engaging and much better at rendering a dimensional soundstage. Now I have no experience with the Underwood modded Unico, nor the newer Unico SE. They've both recieved great reviews, as did the original. I think synergy and personal preferences are going to be a strong determinant of what works for you.
Marco
Marco