The speakers thing was just clarifying that 8 ohms was possible/common.
And, amps are totally unnecessary for this headphone because it has high sensitivity and low impedance. If you use a properly designed amp that will be transparent and not color the sound, it will sound identical to another properly designed amp with higher output power. Unfortunately very few amps are properly designed; any differences you notice are the fault of the equipment, not the headphones.
I think the idea is that adding an external amp probably gets you closer to what you call a "properly designed amp" than the onboard amp of most DAPs.
I also wouldn't be so fast as to say differences are always the amplifier's "fault" either. Certain headphones will pair better with certain amplifier types. I'm certain I could find a great amplifier and a great headphone that don't sound that great together. How each part of the audio chain interacts as a whole is what results in the final fidelity. If an amp and a headphone don't match well, who's fault is it? And how much does that matter?
I think it's more important to see how well a system works rather than a singular device, but that's just one man's perspective.
Apologies to get OT. I don't own this headphone and have nothing to say about it... I just don't think looking at the spec sheet and seeing low impedance and high sensitivity numbers automatically rule out the benefits of amplification. It sounds like some MDR-R1 owner's ears agree with some of the comments regarding how well this headphone scales.