However-3dB is a god guess that’s likely to cover most of them in your record collection . You are right that with a pathological waveform they can get arbitrarily big ( almost ). I usually guess-3,5 dBI didn't say that Inter Sample Peaks don't exist. My point is that if you care about this (because the DAC designer did not), then a margin of -3 dB is no guarantee. Obviously we didn't understand each other too well.
and room fit instructions