It is less about the speaker sounding "optimal", since it is rated to handle 180 W, than how loudly you want to listen. The link I provided also has a comparison table, pasted below, that relates SPL to various real-world examples. I have actually been next to a newspaper press and it is
not something you want to be near without ear protection. Given peaks may be 15~20 dB or so above your average level (headroom), your amp should provide an average level of around 80 dB with 20 dB headroom for peaks, which is very loud to me. I listen around 60 to 70 dB only rarely going louder. Based on that, and assuming you want to retain your hearing in the future, the 120 W/ch WiiM amp should be plenty loud enough. If you found an amp rated for 180 W, the max spec of the R3's, that would only provide a small (<2 dB) increase in volume so I think what you have now should be fine.
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