In the 1960s, my dad gave me a Panasonic receiver with two cube speakers, just in time for the advent of FM stereo radio in the San Francisco Bay Area. Out of the blue one night, he just walked in with it. The receiver allowed me to plug in a record player, though I only had a few LPs. Later, when I went off to college, my mom took me shopping for a new stereo. I chose a Kenwood integrated amplifier—without a tuner but with the capability to plug in a tape deck, which I did. During my undergrad years, it served me well. Later, I switched to an NAD receiver, which allowed me to listen to the radio again.

The Momentum M400 MxV Mono amplifier ($79,500/pair) is the latest iteration of Dan D'Agostino Master Audio Systems' debut amplifier of 2011, the Momentum Mono amplifier. Weighing 95lb, it is smaller and lighter than its entry-level sibling, the more powerful, 125lb Progression M550 Mono amplifier ($47,500/pair), and is veritably dwarfed by some other monoblocks, including the flagship D'Agostino Relentless Epic 1600 (570lb) and the Karan Acoustics POWERa mono (231lb), which I reviewed in May 2023. But if the M400 MxV's rock-solid look and feel and its exquisite aesthetics—a sleek amalgam of silver and copper fronted by a power meter that glows green and radiates Rolex quality—are any indication, a helluva lot is going on beneath its showy exterior.