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This is a buyer’s market at this ask: at US$900, it sits right at the 25th percentile of the recent comps and below the US$1,000 median, so it reads as a solid fair-to-good buy rather than a stretch. If the unit is functioning properly, that’s exactly the kind of price where this model becomes interesting.
The M-504 is well regarded as a hefty, no-nonsense power amp with real current delivery and the kind of drive that suits efficient speakers and tougher loads alike. It has a reputation for sounding authoritative and punchy without fuss, so the upside here is straightforward: a classic high-power stereo amp at a sensible entry point. At this price, the key check is condition—clean cosmetics, stable operation, and no protection issues matter more than chasing perfection.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Onkyo traces its roots to postwar Japan, founded in 1946 in Osaka by Takeshi Goda, an engineer at Matsushita Electric who envisioned high-quality Japanese loudspeakers. Initially established as Osaka Denki Onkyo K.K., the company began production in 1948 with the acclaimed ED-100 speaker featuring a 25 cm driver, quickly building a reputation through LP concerts and innovative designs that resonated with audiophiles.
The brand excels in premium home audio, renowned for AV receivers, hi-fi amplifiers, and surround sound speakers that deliver exceptional clarity and power. Its portfolio spans turntables, DACs, headphones, and cables, bolstered by acquisitions like Pioneer's home electronics division in 2015, enabling cutting-edge integrations such as internet radio and high-resolution streaming.
Onkyo holds a solid mid-tier position in the hi-fi market, prized by discerning buyers for reliable performance and value rather than ultra-high-end exotica. Despite bankruptcy challenges in the late 2010s, its revival under new ownership preserves a legacy of technological innovation and pure sound enjoyment, appealing to both vintage enthusiasts and modern home cinema setups.
See all Onkyo listings on RADAR.
