Believe it or not, I have experienced extremely good results using a plain-old integrated amp with my Mementos - well, maybe not so "plain-old" but an integrated never-the-less.
I'm using a McIntosh MA-7000 and I think the results are phenomenal. I have (current) Spectral separates on another system, I've tried them on the Mementos and I really like the MA-7000 just as well.
I also use a McIntosh MCD500 player and I think the combination is wonderful