I had assumed that they were 5-way binding posts, but further inspection says no. For popularity of interfaces, powered speaker outputs are obviously for compl

I had assumed that they were 5-way binding posts, but further inspection says no. For popularity of interfaces, powered speaker outputs are obviously for completely different use-cases than anything else you listed. You aren't going to connect a 3.5mm or TOSLINK output to a passive speaker, and you generally aren't going to connect speaker-level outputs to an RCA input. The only other competing connecter worth considering is plain old bare wire. It has TOSLINK and HDMI outputs in addition; it's not an either/or choice. As for the benefit of amplifier integration, I can think of a few: - Space. The nice receivers you talk about are generally at least 17" wide and 14" deep, so if this is a bedroom or den setup for wireless music streaming you might not have space for one. Smaller ones obviously exist, but I haven't found one smaller than about 11" by 13" with remote volume control. - Power consumption. Full receivers often have ridiculous idle power consumption, and the only standardized way to turn them off (HDMI-CEC) can still have significant standby power consumption. Also it uses a more efficient class D amp while most full receivers use class AB. - Volume control. It should be between the DAC and amplifier, but with a two piece streaming + outboard receiver your options are either a separate remote to control it or digital volume control at the streamer, which really is suboptimal. And if you want a tiny amp then there is no remote; you have to get up and physically turn a knob.