I own a pair of Guarneri Mementos and also have Spectral electronics (although I usually use those in another system with Avalon Eidolons) I have switched the Mementos into the Spectral system, however, and they sounded phenomenal - to the point where I truly wish I could afford a second batch of Spectral. (I have the DMC30SL and a pair of 360's)
I routinely have the Mementos paired with a McIntosh integrated amp - MA7000 - and the Spectral stuff seemed to add another dimension to the speaker's performance, although they do sound terrific with the MAC.
The Mementos are "easy to drive", but they really come into their own with higher powered amplification. From my own experience, I would recommend at least 200 WPC. On the other hand, they sound good with virtually anything you can throw at them - including tubes - I played mine with a 75 watt tube amp and could have lived with that combination forever.