You can use all HDP of it - aside from the headphone amp and DAC, you can also use its preamp. You can use either a dedicated power amp with passive speakers (no volume pot), or you can use an active speaker where the problem despit having a volume control on them means optimum placement of the monitors usually means putting the knob beyond easy reach (if it wasn't mounted on the plate amp in the rear to begin with).
You can look up Swan active speakers - D1080MkIV goes for $200 and M200MkIII for around $400 I think - and similar brands (Audioengine, Aktimate, etc). Aside from their (the entry level products') definition of "flat" which is a bit warm, which in the absolute lowest price pro audio equivalents tend to be too flat without dynamic range and probably bright-sounding by perception if not also by actual measurement, the more home audio-geared active speakers have a master and slave speaker. That means there is only one stereo (or dual-stereo if driving each transducer type individually) amp in one speaker. While some may contend that it makes the electrical signal asymmetrical with a longer cable running to the slave speaker, it has one convenient advantage : you only run one power cable to the outlet instead of one for each speaker.
I have the older D1080MkII 08 and I can hear house bass pounding in a room across the hall, rattling the walls. Really low, really loud bass at high volumes should distort it but I haven't encountered it yet, so YMMV depending on how loud you'd go (I'm not holding back much though because I hate my next door neighbors' guts).