Welcome.
Selecting speakers would be your next logical move as the only transducer (something that changes energy from one form to another which is much tougher than simply amplifying signal) in a digital system. Recommend reading Floyd Toole's "Sound Reproduction" 3rd edition to learn how speakers/rooms interact. Fit them to the room, which means monitors unless your room is super huge. As Toole indicates distribution of multiple smaller subs is the key to minimize in-room bass peaks/dips (and fits with using monitors). Look hard into active monitors, like the studio professionals do, for better dynamics, flatter frequency response, and deep/full bass on top of wonderful levels of detail.
Take your time shopping for speakers, bring a wide range of your favorite music and take notes which will force you to listen critically. Avoid large, noisy listening venues that don't react like your room and limit the auditions to 3 or 4 a day to avoid listener fatigue. Make sure you can return them if they don't sound right at home. My favorites are JBL 305 Mk2 ($300/pair), 705P ($2000/pair), or the bigger 708P ($4000/pair) which boast having controlled directivity and a deep company resume backing them up.
DAC technology has been moving fast, so don't "over invest" here. The $500 Topping DX7s (measures incredibly well) or $1100 RME ADI-2 (professional, better equipped) are all you need to spend for a solid system and both include a volume control (but no analog inputs).
And don't forget the room. Bigger is better. Properly shaped is even more important (see Toole). But having an insulated, dedicated room can't be beat to allow for listening when you want without sonic interference. Even with a well shaped/sized room treatments help.
Take care.
