When I purchased mine back in 2000, I listened them with a pair of Lamm parallel single-ended amps, some Thor monos, a Simaudio solid-state amp, and my own amp of the time, a McIntosh MC500. I definately preferred both the Sim and the Mac compared to the other two, mainly because of the bass response.
Since then, I've set up these speakers in five different living spaces, and the bass is the aspect of the Mezzos' performance that I'm least happy with . . . they can either get really boomy, or turn around (with position changes, or even different recordings) and sound thin.
The vintage Marantz amps I'm running now are by far the best I've ever heard with these speakers. They're P-P EL34 amps, and unlike most SE designs, maintain a pretty low output impedance. (Amps with higher output impedances are usually associated with the traditional "tubey" sound: relaxed highs, boomier bass).
And one thing I will say is that I have never once wished for my Mezzos to have boomier bass, in any room. Thus, I personally wouldn't be looking at single-ended amps as a good match for them. But as always, your mileage may differ . . .
